102  Steam  Engineering 

684.  Mention    another   safety   device   connected   with 
hydraulic  elevators. 

Ans.  Safety  clamps  under  the  control  of  a  speed  limit 
centrifugal  governor  which  causes  the  clamps  to  grip  the 
guides  and  thus  hold  the  car. 

685.  How  is  this  safety  governor  operated  ? 

Ans.  By  means  of  a  small  cable  connected  with  the  car 
and  moving  with  it,  which  passes  over  the  sheave  pulley 
of  the  governor. 

686.  Why  are  some  elevator  pistons  fitted  with  two  pis- 
ton rods? 

Ans.  To  prevent  the  piston,  and  crosshead  from  turn- 
ing or  twisting,  and  also  to  strengthen  the  construction. 

687.  What  other  methods  are  used  for  manipulating 
the  water  valve,  besides  the  one  already  described? 

Ans.  Running  ropes,  and  standing  ropes,  either  of 
which  may  be  operated  by  means  of  a  lever,  or  wheel  in 
the  car. 

688.  Do  these  devices  directly  operate  the  main  valve? 
Ans.    No.    They  operate  a  small  valve  called  the  pilot 

valve. 

689.  What  is  the  function  of  the  pilot  valve? 

Ans.  When  opened  it  admits  the  pressure  water  to  a 
small  cylinder  with  piston  connected  to  the  main  valve 
stem.  This  actuates  the  main  valve,  which  in  turn,  by  its 
movement,  closes  the  pilot  valve. 

690.  Upon  what  does  the  amount  of  opening  given  the 
pilot  valve,  and  consequently  the  main  valve  depend? 

Ans.  Upon  the  distance  the  lever  in  the  car  is  moved 
from  central  position. 

691.  What  is  meant  by  central  position  of  lever? 


Elevators — Electric  and  Hydraulic  103 

Ans.  That  position  in  which  there  is  no  flow  of  water 
either  into  or  out  of  the  cylinder,  and  the  car  is  moving 
only  by  its  momentum. 

692.  What  is  the  result  of  moving  the  lever  too  quickly 
to  central  position  when  the  car  is  moving  at  a  high 
rate  of  speed? 

Ans.  The  motion  of  the  car  will  be  arrested  with  a 
sudden  jerk. 

693.  How  many  kinds  of  horizontal  hydraulic  elevators 
are  in  use? 

Ans.  Two.  One  is  the  pushing,  and  the  other  the 
pulling  type. 

694.  Describe  the  action  of  the  pushing  type? 

Ans.  The  car  being  at  the  bottom,  the  pressure  water 
is  admitted  behind  the  piston  which  then  moves,  pushing 
the  crosshead  and  cable  sheave  and  lifting  the  car. 

695.  Describe  the  action  of  the  pulling  type? 
Ans.     It  is  the  opposite  of  that  just  described. 

696.  Is  there  much  difference  in  the  valve  mechanism 
of  the  horizontal,  and  vertical  types  of  hydraulic  elevators  ? 

Ans.     Very  little  except  a  few  minor  details. 

697.  "What  is  meant  by  a  double-deck  machine? 

Ans.  Where  the  floor  space  is  restricted  two,  and  some- 
times three  or  four  machines  are  mounted  one  above  the 
other. 

698.  What  water  pressure  is  usually  carried  in  operat- 
ing the  types  of  hydraulic  elevators  that  have  hitherto 
been  described? 

Ans.  Pressures  not  exceeding  200  Ibs.,  the  average  being 
150  Ibs.  per  square  inch. 

699.  Are  any  higher  pressures  than  this  being  used  for 
operating  hydraulic  elevators? 

Ans.     Yes.    Pressures  of  700  to  800  Ibs.  and  higher. 


SWINGLE'S  CATECHISM 

OF 

STEAM,  GAS,  AND  ELECTRIC 
ENGINEERING 


A  complete  Practical  System  of  Instruction  covering  all 
the  important  details  relative  to  the  care  and  operation  of 
Steam  Boilers,  Steam  Engines,  Steam  Turbines,  Air 
Compressors,  Refrigerating  Machinery,  Elevators — both 
Electric  and  Hydraulic,  also  Electric  Machinery,  in- 
cluding Dynamos,  Motors,  Transformers,  Rotary  Con- 
verters, Switch  Boards,  etc. 


Especially  valuable  to  those  contemplating  an  ap- 
pearance before  an  Examining  Board  of  Engineers 

A   Complete   Book  of  Reference  for  the 

Working  Engineer  in  the  daily 

round  of  his  duties. 

BY 

CALVIN    F.    SWINGLE 

Author  of  "Twentieth  Century  Hand  Book  for  Steam  Engineers  and 

Electricians,"    "Encyclopedia  of  Engineering," 

and  "Steam  Turbine  Engines." 


CHICAGO 

FREDERICK  J.  DRAKE  &  COMPANY 

PUBLISHERS 


COPYRIGHT  1910 

BY 
FREDERICK  J.  DRAKE  &  Co. 


Swingle's  Catechism  of  Steam,  Gas, 
and  Electrical  Engineering 


INTRODUCTION 

The  constantly  increasing  demand  for  information  in  a 
condensed  form,  pertaining  to  engineering  topics  has  in- 
duced the  author  to  prepare  this  book,  with  a  view  of 
assisting  his  brother  engineers  in  their  search  for  just  the 
information  that  they  are  looking  for,  and  especially  when 
they  are  in  a  hurry,  and  do  not  have  much  time  to  look 
for  it,  as,  for  instance,  in  an  emergency  due  to  a  break- 
down, the  Catechism  of  Steam,  Gas,  and  Electricity  will  be 
found  to  be  an  invaluable  aid,  for  the  reason  that  it  covers 
practically  the  entire  field  of  Stationary  Engineering,  in- 
cluding not  only  Steam  Boilers  and  Engines,  but,  in  addi- 
tion, Steam  Turbines,  Gas  Engines,  and  Gas  Producers, 
Air  Compressors,  Refrigeration  and  Ice  Making,  Elevators, 
both  Electric  and  Hydraulic,  and  finally, 'the  subjects  of 
Electricity  and  Electric  Machines,  Dynamos,  Motors,  etc. 

The  necessity  for  thorough  and  complete  examinations 
regarding  the  qualifications  of  men  asking  to  be  entrusted 
with  the  care  and  operation  of  power  generators,  whether 
steam,  gas  or  electrical,  is  now  universally  recognized,  and 
as  a  consequence,  all  large  cities  and  towns,  and  a  large 
number  of  states,  have  license  laws,  requiring  engineers  and 
electricians  to  pass  these  examinations  before  being  granted 
license  permitting  them  to  take  charge  of  and  operate  such 

217105 


Introduction 

machinery.  To  those  contemplating  the  taking  of  such  ex- 
aminations, the  questions  and  answers  following  will  prove 
to  be  a  most  valuable  helper,  as  it  furnishes  the  much 
sought-f or  information  in  plain,  easily  understood  language, 
the  answers  being  condensed  in  such  form  as  to  enable  the 
applicant  for  license  to  memorize  them  without,  any  diffi- 
culty whatever,  and  thus  be  .able  to  qualify  himself  for  the 
position  sought  for.  This  Catechism  thus  serves  the  double 
purpose  of  being  an  assistant  to  the  working  engineer,  and 
also  a  helper  to  the  man  who  aspires  to  become  an  engineer. 

CALVIN  F.  SWINGLE. 


Types  of  Boilers 


1.  What  types  of  boilers  are  most  commonly  used  for 
stationary  work? 

Ans.  The  horizontal  tubular  boiler  and  the  water-tube 
boiler. 

2.  Describe  in  general    terms   the   horizontal   tubular 
boiler. 

Ans.  It  consists  of  a  shell  having  tubes  of  small  diam- 
eter, extending  from  head  to  head. 

These  tubes  are  located  in  the  water  space. 

3.  What  is  their  function? 

Ans.  To  supply  a  passageway  to  the  stack  for  the  hot 
gases  from  the  furnace. 

4.  Does  the  water  in  the  boiler  receive  heat  from  these 
tubes? 

Ans,    It  certainly  does. 

5.  Describe  the  route  taken  by  the  smoke  and  hot 
gases  in  the  operation  of  a  tubular  boiler. 

Ans.  From  the  furnace,  located  under  the  front  end 
of  the  boiler,  the  gases  pass  under  and  along  the  sides  of 
the  shell,  back  to  the  rear  end,  the  upper  part  of  which  is 
arched  over.  The  route  is  here  reversed,  and  the  products 
of  combustion  return  through  the  flues  towards  the  front 
end  and  thence  through  the  breeching  into  the  stack. 

6.  Is  this  type  of  boiler  economical  in  the  burning  of 
fuel? 

Ans.  It  can  be  made  so  if  properly  set  and  handled  in 
operation. 

7.  Describe  in  a  general  way  the  water-tube  boiler. 
Ans.    It  consists  of  a  set,  or  sets  of  tubes  3  to  4  inches 

in  diameter,  sometimes  vertical,  and  sometimes  inclined, 

5 


6  Steam  Engineering 

and  connected  at  the  top  to  a  steam  drum,  and  at  the  bot- 
tom to  a  mud  drum. 

8.  What  advantages  as  regards  circulation  of  the  water 
has  the  water  tube  boiler? 

Ans.    It  provides  for  a  free  circulation. 

9.  Name  another  advantage  connected  with  the  water 
tube  boiler. 

Ans.    The  margin  of  safety  from  dangerous  explosions, 

10.  Why  is  this? 

Ans.  Because  if  one  or  more  tubes  gives  way  the  pres- 
sure is  relieved. 

11.  What  precautions  should  be  observed  in  the  design 
and  construction  of  a  boiler? 

Ans.  The  best  materials  should  be  used,  the  boiler 
should  be  simple  in  design,  and  the  workmanship  should  be 
perfect. 

12.  Where  should  the  mud  drum  be  located  ? 

Ans.    In  a  place  removed  from  the  action  of  the  fire. 

13.  What  should  be  the  capacity  of  the  boiler  relative 
to  its  work? 

Ans.  It  should  have  a  steam  and  water  capacity  suf- 
ficient to  prevent  any  fluctuation  in  either  the  steam  pres- 
sure, or  the  water  level,  if  properly  fed. 

14.  Why  should  the  water  in  a  boiler  circulate  freely 
and  constantly? 

Ans.  In  order  to  maintain  all  parts  at  as  near  the  same 
temperature  as  possible. 

15.  What  should  the  strength  of  a  boiler  be,  relative  to 
the  strain  it  is  liable  to  be  subject  to? 

Ans.    It  should  have  a  great  excess  of  strength, 

16.  Is  a  combustion  chamber  an  advantage  to  a  boiler? 


Types  of  Boilers  7 

Ans.    It  is,  in  order  to  complete  the  combustion  of  the 
gases  before  they  escape  to  the  chimney. 

17.  How  should  a  boiler  be  arranged  with  regard  to 
cleaning  ? 

Ans.    All  parts  should  be  easily  accessible  for  cleaning 
and  repairs. 

18.  What  type  of  boiler  is  the  Cahall? 
Ans.    It  is  a  water-tube  boiler. 

19.  Is  it  vertical  or  horizontal? 
4ns.     It  is  built  either  way. 

20.  What  form  of  Cahall  is  generally  used  in  central 
power  stations? 

Ans.     The  horizontal  form. 

20a.     What  is  the  range  of  pressures  that  these  boilers 
are  built  for? 

Ans.     From  160  to  500  pounds  per  square  inch, 

21.  Describe  the  method  of  constructing  the  joints. 
Ans.     The  sheets  are  beveled  on  the  edges,  bent  into 

shape,  and  rivet  holes  drilled  after  bending. 

22.  What  is  gained  by  so  doing? 

Ans.     Absolutely  round  rivet  holes  and  no  crystalliza- 
tion. 

23.  What  type  of  riveted  joint  is  usei  on  the  higher 
pressure  boilers? 

Ans.    Triple  riveted,  double  strapped. 

24.  How  are  the  tubes  connected  to  the  steam  drum 
in  the  Cahall  boiler? 

Ans.     By  nipples  connected  to  saddles  on  the  drum. 

25.  Does  this  boiler  rest  upon  the  brick  work? 

Ans.     It  does  not,  but  is  suspended  free  from  the  ma- 
sonry. 

26.  What  advantage  is  there  in  this  style  of  setting? 


8  Steam  Engineering 

Ans.  The  entire  structure  is  free  to  expand  or  contract 
without  causing  any  strains  on  either  boiler  or  brick  work. 

27.  Describe  the  Heine  boiler. 

Ans.  It  consists  of  one,  and  sometimes  two  shells  on 
drums  resting  upon  water  legs  riveted  to  each  end.  These 
water  legs  are  connected  by  horizontal  tubes.  The  water 
fills  the  tubes,  water  legs,  and  partially  fills  the  shell,  leav- 
ing the  upper  portion  for  steam  space. 

28.  In  the  setting  does  this  boiler  occupy  a  horizontal 
position  ? 

Ans.  No.  The  shell  and  tubes  have  an  incline  of  one 
inch  in  twelve  from  front  to  rear. 

29.  What  provision  is  made  for  cleaning  and  repairing 
the  tubes  ? 

Ans.  Hand-holes  are  located  in  the  head  plates  oppo- 
site each  tube. 

30.  How  are  these  hand-holes  closed? 
Ans.    In  the  ordinary  way,  by  plates. 

31.  Where  is  the  mud  drum  located  in  the  Heine  boiler  ? 
Ans.    Inside  the  shell,  near  the  bottom. 

32.  How  is  the  Heine  boiler  supported  in  the  setting? 
Ans.    The  front  or  fixed  end  rests  upon  cast  iron  col- 
umns.   The  rear  water  leg  upon  rollers. 

33.  Describe  in  brief  the  Babcock  &  Wileox  boiler. 
Ans.    It  is  composed  of  wrought  iron  tubes,  placed  in 

an  inclined  position,  and  connected  with  each  other,  and 
with  a  horizontal  steam,  and  water  drum  by  vertical  headers. 

34.  Where  is  the  mud  drum  in  this  boiler  ? 

Ans.  In  the  rear,  and  connected  to  the  lowest  part  of 
the  boiler. 

35.  What  provision  is  made  for  cleaning  the  tubes  in 
the  Babcock  &  Wilcox  boiler? 


Types  of  Boilers  9 

Ans.  Through  hand-holes  in  the  headers,  opposite  each 
tube. 

36.  How  is  this  boiler  supported  in  the  setting? 

Ans.  It  is  suspended  from  wrought  iron  girders,  en- 
tirely independent  of  the  brick  work. 

37.  Describe  in  general  terms  the  Stirling  boiler, 
Ans.     It  consists  of  three  upper  steam  drums,  each  be- 
ing connected  by  a  number  of  tubes  to  a  lower  or  mud 
drum. 

38.  How  are  the  steam  spaces  connected? 
Ans.     By  shorter  tubes. 

39.  How  is  the  boiler  supported? 
Ans.     On  a  structural  steel  frame  work. 

40.  What  provision  is  made  for  expansion  and  contrac- 
tion of  the  tubes  ? 

Ans.     They  are  slightly  curved  near  the  ends. 

41.  How  are  the  hot  gases  directed  in  their  course 
from  furnace  to  stack? 

Ans.     By  means  of  fire  brick  baffle  walls. 

42.  How  is  the  interior  of  this  boiler  cleaned? 

Ans.  Four  manholes  are  provided  in  the  drums,  by 
which  access  to  the  interior  of  both  the  drums  and  tubes  is 
obtained. 

43.  What  type  of  boiler  is  the  Maxim  boiler? 

Ans.  It  is  a  water-tube  boiler  consisting  of  two  drums, 
one  above  the  other,  connected  by  tubes. 

44.  Describe  the  tubes. 

Ans.  Each  tube  has  two  bends,  thus  providing  for  un- 
equal expansion  or  contraction. 

45.  How  is  the  heating  surface  of  the  Maxim  boiler 
arranged  ? 


10  Steam  Engineering 

Ans.  It  is  so  arranged  that  the  current  of  heated  gases 
is  made  to  travel  three  times  the  length  of  the  tubes,  the 
direction  of  the  current  heing  changed  seven  times  in  its 
route  from  furnace  to  stack. 

46.  What  can  be  said  of  the  Bigelow-Hornsby  water- 
tube  boiler? 

Ans.  ©wing  to  the  flexible  form  of  its  construction  it 
is  possible  to  build  it  in  very  large  units,  2,000  horsepower 
and  upwards. 

47.  What  peculiar  feature  makes  this  possible? 

Ans.  Each  section  is  independent  of  its  neighbor,  ex- 
cept the  nipples  connecting  with  the  steam  drum,  and  the 
equalizing  nipples  connecting  the  bottom  drums  of  the 
rear  sections. 

48.  How  is  the  boiler  supported  ? 
Ans.     Entirely  from  overhead  beams, 

49.  What  percentage  of  the  heating  surface  do  the  tubes 
of  the  front  unit  comprise? 

Ans.    More  than  12  per  cent. 

50.  Where  is  the  feed  water  first  admitted? 
Ans.     Into  the  bottom  drum  of  the  rear  unit. 

51.  Describe  the  course  of  the  feed  water. 

Ans.  The  feed  water  is  admitted  into  the  bottom  drum 
of  the  rear  unit,  and  is  advanced  gradually  from  the  coldest 
to  the  hottest  portion  of  the  boiler. 

52.  How  is  the  speed  of  the  feed  water  up  the  rear  unit 
regulated  ? 

Ans.  By  the  amount  of  steam  generated,  ample  time 
being  permitted  for  scale  forming  matter  to  be  deposited 
in  the  bottom  drum  of  this  unit. 

53.  Where  does  the  liberation  of  steam  take  place  ? 
Ans.     In  the  upper  drum. 


Types  of  Boilers  11 

54.  What  can  be  said  of  this  boiler  regarding  the  utili- 
zation of  the  heat? 

Ans,  It  is  baffled  so  that  the  products  of  combustion 
are  carried  uniformly  over  the  heating  surfaces  in  thin 
layers,  the  baffle  plates  serving  to  guide  the  gases  through  in 
substantially  uniform  passages. 

55.  To  what  factor  of  safety  is  the  Bigelow-Hornsby 
boiler  built? 

Ans.    Five  for  200  pounds  working  pressure. 

56.  Describe  in  brief  the   Wickes   vertical   water-tube 
boiler. 

Ans.  It  consists  of  two  cylinders  joined  together  end- 
ways by  straight  tubes,  and  erected  in  a  vertical  position. 

57.  What  can  be  said  of  the  top  cylinder? 

Ans.    It  is  the  longer,  and  is  designated  the  steam  drum. 

58.  What  about  the  bottom  cylinder? 

Ans.  It  is  the  shorter,  and  is  designated  the  mud  drum. 
Both  cylinders  vary  in  dimensions  as  to  diameter  and 
length,  according  to  the  power  required  of  the  boiler. 

59.  Where  are  the  manholes  of  the  Wickes  boiler  ? 
Ans.     One  is  placed  in  the  convex  head  of   the   steam 

drum;  there  are  also  a  number  of  hand-holes  in  this  head. 
A  manhole  is  also  placed  in  the  lower  or  mud  drum,  near 
the  floor,  thus  permitting  access  to  the  top  and  bottom  of 
the  boiler, 

60.  How  are  these  tubes  divided? 

Ans.  By  heavy  fire-clay  tile  these  tubes  are  divided  into 
two  compartments.  Those  tubes  in  the  front  compart- 
ment are  called  the  "risers"  and  those  in  the  rear  the 
"downcomers." 

61.  What  can  be  said  of  the  heat  in  its  double  passage? 


12  Steam  Engineering 

Ans.  It  surrounds  completely,  and  closely  the  tubes  in 
both  compartments. 

62.  Where  is  the  water  line  in  this  boiler? 

Ans.  At  a  sufficient  height  in  the  steam  drum  to  in- 
sure the  complete  submersion  of  all  the  tubes. 

63.  How  is  the  brick  work  setting  of  the  Wickes  water- 
tube  boiler  arranged? 

Ans.  It  is  independent  of  the  weight  of  the  boiler,  and 
free  to  expand  or  contract. 

64.  Describe  briefly  the  design  of  the  Atlas  water-tube 
boiler. 

Ans.  It  consists  mainly  of  three  drums  and  two  water 
legs  extending  crosswise,  while  the  tubes  extend  lengthwise. 

65.  What  is  the  original  feature  in  the  design  of  the 
water  legs? 

Ans.  They  are  formed  by  the  continuation  of  front 
and  rear  shell  plates. 

66.  What  other  valuable  feature  is  claimed  for  this 
boiler? 

Ans.  After  the  steam  leaves  the  vessels  containing  water 
it  is  passed  through  a  series  of  superheating  tubes,  and  is 
superheated. 

67.  Describe  the  course  of  the  feed  water. 

Ans.  It  is  fed  first  into  the  purifier,  whence  it  over- 
flows into  the  rear  drum  and  down  into  the  rear  leg,  thence 
through  the  inclined  tubes  to  the  front  leg,  thence  up  into 
the  front  drum,  where  the  steam  is  liberated  and  carried 
through  superheating  tubes  to  the  steam  drum. 

68.  What  are  the  facilities  for  cleaning  the  water  tubes 
of  this  boiler? 

Ans.  An  individual  hand-hole  is  located  opposite  each 
end  of  each  water  tube. 


Types  of  Boilers  13 

69.  How  is  the  interior  of  each  of  the  three  cross  drums 
reached  ? 

Ans.     Through  a  large  manhole  in  each  end. 

70.  Describe  briefly  the  design   and  construction   of 
the  Marzolf  water-tube  boiler. 

Ans.  It  consists  of  three  drums  connected  with  each 
other  in  triangular  form.  Drum  A  directly  over  the  fire 
is  connected  by  tubes  with  drum  B  above  it,  and  with  drum 
C  in  the  rear  and  slightly  below  it.  Drum  C,  which  is  the 
mud  drum,  is  also  connected  with  drum  B.  The  tubes  are 
each  slightly  bent.  The  steam  is  collected  in  drum  B,  which 
is  maintained  about  one-third  full  of  water. 

71.  Describe  in  brief  the  action  of  the  heat  upon  this 
boiler. 

Ans.  It  acts  first  upon  the  water  in  drum  A  over  the 
furnace,  then  by  means  of  a  baffle  wall  it  is  carried  along 
the  inclined  tubes  to  drum  B,  where  it  is  deflected  and  car- 
ried down  along  other  inclined  tubes  to  drum  C,  thence  to 
the  stack. 

71.  How  are  the  products  of  combustion  caused  to  act 
upon  the  lower  bank  of  tubes? 

Ans.  By  means  of  baffle  walls  located  in  the  rear  of 
the  furnace. 

72.  At  what  point  in  this  boiler  is  the  feed  water  ad- 
mitted? 

Ans.    At  the  lowest  point,  viz.,  the  mud  drum. 

73.  What  are  the  principal  advantages  claimed  for  the 
Duplex  water-tube  boiler? 

Ans.  Delivery  of  superheated  steam;  the  removal  of 
steam  from  the  boiler  at  a  point  where  there  is  no  ebul- 
lition; the  drums  not  exposed  to  the  direct  action  of  the 
fire. 


14  Steam  Engineering 

74.  Describe  in  brief  the  design  of  this  boiler. 

Ans.  Two  upper  steam  drums  connected  by  tubes,  a 
mud  drum  at  the  bottom  and  rear  which  is  connected  to 
the  upper  drums  by  headers  and  short  nipples.  The  tubes 
are  inclined  20  degrees  to  insure  rapid  and  positive  cir- 
culation. 

75.  How  is  this  boiler  supported? 
Ans.    Upon  a  heavy  steel  framework. 

76.  What  is  the  leading  feature  in  connection  with 
the  Erie  City  water-tube  boiler? 

Ans.  The  three  banks  of  tubes  are  practically  vertical, 
connected  to  upper,  and  lower  drums,  and  spaced  so  that  any 
one  of  them  may  be  cut  out  for  repairs  without  interfering 
with  the  others. 

77.  How  do  the  products  of  combustion  act  upon  this 
boiler? 

Ans.  The  baffling  is  arranged  to  pass  three  times  across 
the  tubes,  and  at  each  end  of  the  upper  drum  is  a  dry 
chamber. 

78.  Describe  in  brief  the  best  method  of  supporting 
horizontal  tubular  boilers. 

Ans.  By  means  of  hangers  suspended  from  I  beams, 
supported  by  cast  iron  columns.  This  takes  the  weight  off 
the  side  walls. 

79.  What  three  principles  should  govern  the  design 
and  construction  of  steam  boilers? 

Ans.  First:  They  should  be  absolutely  safe.  Second: 
They  should  be  economical  in  the  consumption  of  fuel. 
Third:  They  should  be  capable  of  furnishing  dry  steam. 

80.  What  is  meant  by  the  term  tensile  strength  as  ap- 
plied to  boiler  material  ? 


Types  of  Boilers  15 

Ans.  The  number  of  pounds  of  pull  that  would  be 
required  to  break  a  bar  of  the  material  in  the  direction  of 
its  length. 

81.  What  is  liable  to  occur  in  case  the  tensile  strength 
is  too  high  ? 

Ans.  Cracking  of  the  sheets,  also  certain  changes  in  the 
physical  properties  of  the  metal. 

82.  Which  are  the  stronger,  punched  or  drilled  plates? 
Ans.    If  the  material  is  good  soft  steel,  punched  plates 

show  a  greater  shearing  resistance. 

83.  What  should  be  the  tensile  strength  of  rivet  iron? 
Ans.    About  60,000  pounds  per  square  inch. 

84.  What  is  a  good  test  for  a  %-inch  rivet? 

Ans.  It  should  stand  being  doubled  up  and  hammered 
together  cold  without  being  fractured. 

85.  What  is  the  shearing  resistance  of  iron  rivets  ? 
Ans.    About  85  per  cent  of  the  original  bar. 

86.  What  is  the  shearing  resistance  of  steel  rivets? 
Ans.    77  per  cent  of  the  original  bar. 

87.  What  is  meant  by  efficiency  of  the  joint? 

Ans.  The  percentage  of  strength  of  the  ttolid  plate,  that 
is  retained  in  the  joint. 

88.  What  should  be  the  style  of  joint  with  sheets  thicker 
than  %  inch? 

Ans.    It  should  be  a  double  butt  joint. 

89.  What  should  be  the  ratio  of  diameter  of  rivet  to 
thickness  of  plate  for  double  butt  joints? 

Ans.  The  diameter  of  the  rivet  should  be  about  1.8 
times  the  thickness  of  sheet. 

90.  What  should  be  the  pitch  of  rivets? 


16  Steam  Engineering 

Ans.    Three  and  one-half  to  four  times  the  diameter  of 
the  hole. 

91.  Describe  the  triple  riveted  butt  joint. 

Ans.     It  has  two  welts  or  straps,  one  inside,  and  one 
outside. 

92.  Is  this  a  good  form  of  joint? 
Ans.     It  is. 

93.  What  type  of  joint  gives  the  highest  efficiency  ? 
Ans.     A  joint  in  which  the  tensile  strength  of  the  rods 

from  which  the  rivets  are  cut  approaches  that  of  the  plates, 
and  when  the  proportions  of  the  joint  are  such,  that  the 
tensile  strength  of  the  rivets,  and  the  crushing  resistance 
of  the  rivets  and  plate,  for  a  given,  or  unit  strip,  are  as 
nearly  equal  as  it  is  possible  to  make  them. 

94.  In  how  many  ways  may  failure  occur  in  a  double 
riveted  butt  joint? 

Ans.     In  five  distinct  ways. 

95.  Name  the  first  manner  of  failure. 

Ans.    Tearing  of  the  plate  at  outer  row  of  rivets. 

96.  What  is  the  second? 

Ans.     Shearing  two  rivets  in  double  shear,  and  one  in 
single  shear. 

97.  What  is  the  third  manner  of  failure? 

Ans.    Tearing  of  the  plate  at  inner  row  of  rivets,  and 
shearing  one  rivet  in  the  outer  row. 

98.  Describe  the  fourth  method  of  failure. 
Ans.     Crushing  in  front  of  three  rivets. 

99.  What  is  the  fifth  manner  of  failure? 

Ans.     Crushing  in  front  of  two  rivets,  and  shearing  one. 

100.  How  may  a  triple  riveted  butt  joint  fail? 


Types  of  Boilers  17 

Ans.  First:  By  tearing  the  plate  at  the  outer  row  of 
rivets.  Second:  By  shearing  four  rivets  in  double  shear, 
and  one  in  single  shear.  Third:  Eupture  of  the  plate  at 
the  middle  row  of  rivets,  and  shearing  one  rivet.  Fourth : 
Crushing  in  front  of  four  rivets,  and  shearing  one  rivet. 

101.  What  is  the  efficiency  of  the  quadruple  riveted 
butt  joint? 

Ans.     In  some  cases  as  high  as  94  per  cent. 

102.  In  what  four  ways  may  failure  occur  in  this  type 
of  joint? 

Ans.  First:  By  tearing  the  plate  at  the  outer  row  of 
rivets.  Second:  By  shearing  eight  rivets  in  double  shear, 
and  three  in  single  shear.  Third :  By  tearing  at  inner  row 
of  rivets,  and  shearing  three  rivets.  Fourth :  By  tearing  at 
first  outer  row  of  rivets  where  the  pitch  is  7%  inches. 

103.  What  is  implied  in  the  staying  of  a  flat  surface? 
Ans.     Holding  it  against  pressure  at  a  series  of  isolated 

points,  which  are  arranged  in  symmetrical  order. 

104.  Does  the  cylindrical  shell  of  a  boiler  need  bracing? 
•Ans.     No. 

105.  Why  is  this? 

Ans.  Because  the  internal  pressure  tends  to  keep  it 
cylindrical. 

106.  How  are  the  heads  sometimes  stayed? 

Ans.  By  through  stay  rods  of  soft  steel,  or  iron  1%  or 
2  inches  in  diameter  extending  through  from  head  to  head. 

107.  What  advantage  has  this  form  of  stays? 
Ans.     The  pull  is  at  right  angles  to  the  plate. 

108.  What  other  methods  of  bracing  the  heads  of  high 
pressure  boilers  are  used? 

Ans.     Gusset  stays,  and  dished  heads. 


18  Steam  Engineering 

109.  What  is  the  minimum  factor  of  safety  for  stays, 
and  braces? 

Ans.    Eight. 

110.  Give  a  simple  rule  for  finding  the  bursting  pres- 
sure of  unstayed  flat  surfaces. 

Ans.  Multiply  the  thickness  of  the  plate  in  inches  by 
ten  times  the  tensile  strength  and  divide  the  product  by 
the  area  of  the  surface  in  square  inches. 


OF  THE  \ 

UNIVERSITY  1 

OF 


Boiler  Setting  and  Equipment 

111.  What  two  methods  of  support  are  generally  used 
in  the  setting  of  horizontal  tubular  boilers  ? 

Ans.  First:  By  suspension  from  I  beams  and  girders, 
and  secondly  by  means  of  brackets  riveted  to  the  side  sheets, 
and  resting  upon  the  side  walls. 

112.  How  are  water  tube  boilers  usually  supported  in 
the  setting? 

Ans.    By  suspension. 

113.  What  important  details  should  be  looked  after 
concerning  the  brick  work? 

Ans.  The  foundations  should  be  good,  and  the  walls 
built  in  such  manner  as  to  take  care  of  the  expansion  and 
contraction. 

114.  How  is  this  accomplished? 

Ans.  By  leaving  an  air  space  of  two  inches  in  the  side 
and  rear  walls  beginning  at  the  level  of  the  grate  bars,  and 
extending  up  to  about  the  center  line  of  the  boiler. 

115.  What  kind  of  brick  should  be  used  for  inside 
lining? 

Ans.     Fire  brick  of  good  quality. 

116.  How  should  bridge  walls  be  built  for  horizontal 
tubular  boilers? 

Ans.     Straight  across  from  wall  to  wall. 

117.  About  what  distance  from  the  bottom  of  the  boiler 
should  this  wall  be  ? 

Ans.    Eight  to  ten  inches. 

19 


20  Steam  Engineering 

118.  Where  is  the  combustion  chamber? 
Ans.     It  is  the  space  back  of  the  bridge  wall. 

119.  How  should  boiler  walls  be  secured? 

Ans.  By  means  of  tie  rods  extending  the  entire  length, 
and  breadth  of  the  setting. 

120.  What  are  the  buck  stays? 

Ans.  They  are  strong  cast-iron,  or  wrought-iron  bars 
placed  vertically  upon  the  outside  of  the  walls,  and  secured 
to  the  tie  rods. 

121.  Should  horizontal  tubular  boilers  be  set  perfectly 
level  lengthwise? 

Ans.  It  is  better  that  they  be  set  about  one  inch  lower 
at  the  back  end,  than  at  the  front  end. 

122.  Give  one  of  the  main  reasons  for  this  style  of 
setting. 

Ans.  When  washing  out  the  boiler,  the  mud  and  water 
will  more  easily  drain  towards  the  blow  off  pipe. 

123.  What  is  the  usual  ratio  of  grate  surface  to  heating 
surface  ? 

Ans,  One  square  foot  of  grate  surface  to  each  36  square 
feet  of  heating  surface. 

124.  At  what  point  should  the  glass  water-gauge  be 
located? 

Ans.  In  such  a  position  as  to  bring  the  lowest  visible 
portion  of  the  gauge  glass  exactly  on  a  level  with  the  top  of 
the  upper  row  of  tubes  of  a  horizontal  tubular  boiler.  With 
other  types  of  boilers  the  lowest  end  of  the  gauge  glass 
should  always  be  on  a  level  with  the  danger  point. 

125.  Why  sHould  the  above  rules  be  observed  in  locating 
a  water  column  ? 


Boiler  Setting  and  Equipment  21 

Ans.  Because  when  the  water  level  in  the  glass  begins 
to  draw  near  to  the  lower  end  of  glass  the  engineer  or  water 
tender  will  have  an  infallible  guide  to  warn  him  to  get 
busy. 

126.  "What  is  a  good  indication  that  the  connections  of 
the  water  glass  are  choked  or  plugged  with  scale  ? 

Ans.  When  there  is  no  movement  of  the  water  in  the 
glass. 

127.  Why  should  there  be  a  trap,  or  siphon  in  the  pipe 
connecting  the  steam  gauge  to  the  boiler? 

Ans.  To  prevent  the  hot  steam  from  coming  into  con- 
tact with  the  spring  of  the  gauge. 

128.  How  may  the  steam  gauge,  and  safety  valve  be 
tested  in  comparison  with  each  other? 

Ans.  By  occasionally  raising  the  steam  pressure  high 
enough  to  cause  the  valve  to  open  at  the  point  for  which 
it  is  set  to  blow. 

129.  Is  the  pop  valve  reliable  as  a  safety  valve  ? 

Ans.  It. is,  if  not  allowed  to  stand  idle  too  long  and 
become  rusty, 

130.  How  often  should  it  be  allowed  to  blow  off? 
Ans.    At  least  twice  a  week. 

131.  Are  lever  safety  valves  used  to  any  extent? 

Ans.  They  are  still  in  use  to  some  extent,  but  are  rapidly 
being  superseded  by  pop  valves. 

132.  What  is  the  function  of  a  fusible  plug? 

Ans.  The  fusible  alloy  of  which  it  is  composed  will  melt 
when  it  comes  in  contact  with  dry  steam,  and  allow  the 
steam  to  blow  a  warning. 

133.  Where  is  the  fusible  plug  located? 


22  Steam  Engineering 

Ans.  In  that  portion  of  the  heating  surface  of  a  boiler 
which  is  first  liable  to  be  overheated  from  lack  of  water. 

134.  Are  Domes  and  Mud  drums  necessary  parts  of 
boilers  ? 

Ans.    They  are  not  as  a  rule. 

135.  Where  should  the  blow  off  pipe  always  be  con- 
nected? 

Ans.    With  the  lowest  part  of  the  water  space. 

136.  Should  the  blow  off  cock  be  opened  while  the 
boiler  is  under  pressure? 

Ans.    Yes,  for  a  few  seconds,  once,  or  twice  each  day. 

137.  Is  a  surface  blow  off  any  advantage? 
Ans.    It  is,  especially  if  the  water  is  muddy. 

138.  What  precautions  should  be  observed  with  regard 
to  inlet  for  feed  water? 

Ans.  The  feed  water  should  not  be  allowed  to  come 
directly  in  contact  with  the  hot  boiler  sheets  until  its 
temperature  is  equal  to,  or  near  that  of  the  water  within 
the  boiler. 

139.  How  may  this  be  brought  about? 

Ans.  By  means  of  feed  water  heaters,  and  internal  coils 
of  pipe  through  which  the  feed  water  is  caused  to  pass. 

140.  What  is  the  most  economical  style  of  feed  pump? 
Ans.    The  belt-driven  power  pump. 

141.  Is  it  the  most  reliable,  or  safest? 
Ans.    It  is  not. 

142.  What  is  the  most  reliable  boiler  feeding  device,  for 
all  conditions  of  stationary  practice? 

Ans.     The  double  acting  steam  pump. 


Boiler  Setting  and  Equipment  23 

143.  What  precautions  should  be  observed  in  figuring 
on  the  capacity  of  a  feed  pump  for  a  battery  of  two  or 
more  boilers?  *',*>->         *-« 

Ans.  To  take  into  account  the  total  quantity  of  water 
required  by  all  of  the  boilers;  and  let  the  capacity  of  the 
pump  be  equal  to  it. 

144.  In  connection  with  feed  apparatus  for  boilers, 
what  other  fittings  and  devices  should  be  installed? 

Ans.  There  should  be  a  tee  located  in  the  horizontal 
section  of  the  feed  pipe  near  the  check  valve,  and  between  it 
and  the  feed  pump.  One  opening  of  this  tee, is  to  be  re- 
duced to  %  or  %  inch  to  receive  a  hot  water  thermometer 
for  testing  the  temperature  of  the  feed  water  when  making 
evaporative  tests,  etc. 

145.  What  other  provisions  along  this  line  should  be 
made? 

Ans.  Tanks  for  weighing  the  feed  water — also  a  sep- 
arate feed  pipe  to  the  boiler  under  test,  also  means  for 
weighing  the  coal  burned  during  test. 

146.  Is  the  injector  an  efficient  boiler  feetier? 

Ans.  It  is  in  locations  where  there  is  not  very  much 
exhaust  steam  available  for  heating  the  feed  water. 

147.  When,  and  by  whom  was  the  injector  invented  ? 
Ans.    In  the  year  1858,  by  Henri  Giffard. 

148.  Why  does  an  injector  force  water  into  a  boiler 
that  is  under  steam  pressure? 

Ans.  Because  the  steam  passing  through  the  injector 
imparts  sufficient  velocity  to  the  water  to  overcome  the 
boiler  pressure. 

149.  Why  does  an  injector  lift  water  from  a  lower  level  ? 


Ans.  Because  the  condensation  of  the  steam  in  the  com 
bining  tube  creates  a  vacuum  there,  and  in  the  suctioi 
pipe  connected  with  it. 

150.  How  may  the  size  of  the  steam  header  for  a  batter} 
of  boilers  be  determined? 

Ans.  The  sectional  area  of  the  header  should  equal  01 
slightly  exceed  the  sum  of  the  areas  of  all  the  boiler  outlets 
to  be  connected  with  it. 

151.  Where  should  all  connections  except  for  drainage, 
enter,  and  leave  the  main  header? 

Ans.    At  the  top. 

152.  How  many  valves  should  there  be  in  each  boiler 
connection  leading  to  the  header  ? 

Ans.    Never  less  than  two. 

153.  What  kind  of  valves  are  best  for  this  purpose? 
Ans.    Automatic  stop,  and  check  valves. 

154.  What  is  the  most  efficient  type  of  superheater  for 
practical  purposes? 

Ans.    The  one  that  is  contained  within  the  boiler  setting. 

155.  How  is  the  velocity  of  flow,  or  piston  speed  per 
minute  of  a  pump  ascertained? 

Ans.  Multiply  number  of  strokes  per  minute  by  length 
of  stroke  in  feet,  or  fractions  thereof. 

156.  The  piston  speed  being  known,  how  is  the  velocity 
of  flow  in  the  discharge  pipe  found  ? 

Ans.    The  velocity  of  flow  in  the  discharge  pipe  is  in 
•  inverse  ratio  to  the  squares  of  the  diameters  of  the  pipe  and 
the  water  cylinder  of  pump. 

157.  When  it  is  required  to  discharge  a  certain  quantity 
of  water  from  a  given  size  of  pipe  in  a  given  time,  how 
may  the  velocity  of  flow  in  feet  per  minute  be  found  ? 


Boiler  Setting  and  Equipment  25 

Ans.  Multiply  the  number  of  cubic  feet  to  be  discharged 
by  144  and  divide  by  area  of  pipe  in  inches. 

158.  When  the  volume  of  water  to  be  discharged  and 
the  velocity  of  flow  are  known,  how  is  the  area  of  the  pipe 
obtained  ? 

Ans.  Multiply  volume  in  cubic  feet  by  144,  and  divide 
by  velocity  in  feet  per  minute. 

159.  What  is  meant  by  "acceleration  of  gravity,"  and 
what  constant  number  represents  it  in  connection  with 
hydraulics  ? 

Ans.  Acceleration  of  gravity  is  the  increase  in  velocity 
caused  by  the  actual  weight  of  the  water,  and  is  represented 
by  the  constant  32. 

160.  What  per  cent  of  allowance  is  ordinarily  made  for 
friction  in  water  pipes? 

Ans.    A  deduction  of  25  per  cent  is  sufficient. 


Feed  Water  Heaters 

161.  Is  a  feed  water  heater  an  economical  factor  in  the 
equipment  of  a  boiler  plant? 

Ans.  It  certainly  is,  provided  exhaust  steam  is  used  for 
heating. 

162.  How  many  kinds  of  exhaust  heaters  are  there? 
Ans.    Two,  viz.:    Open,  and  closed. 

163.  Describe  in  brief  terms  the  action  of  a  so-called 
open  heater. 

Ans.  The  exhaust  steam  mingles  directly  with  the 
water,  and  a  portion  of  it  is  condensed. 

164.  Describe  the  operation  of  a  closed  heater. 

Ans.  The  exhaust  steam  and  the  water  are  kept  sep- 
arate. In  some  cases  the  steam  passes  through  tubes  that 
are  surrounded  by  water,  and  in  other  types  the  water 
fills  the  tubes  that  are  surrounded  by  steam. 

165.  What  difference  exists  between  the  two  kinds  of 
heater? 

Ans.  The  closed  heater  is  under  full  boiler  pressure 
when  the  feed  pump  is  working,  while  the  open  heater  is 
not  because  the  feed  pump  is  between  it  and  the  boiler. 

166.  What  per  cent  of  saving  in  fuel  may  be  effected 
by  the  use  of  a  heater? 

Ans.    Prom  12  to  15  per  cent. 

167.  Of  what  capacity  should  a  feed  water  heater  be, 
relative  to  the  boilers  ? 

Ans.  It  should  have  capacity  sufficient  to  supply  the 
boilers  for  15  or  20  minutes. 

27 


28  Steam  Engineering 

168.  Can   the  exhaust   injector  be   used   for   feeding 
boilers. 

Ans.  It  can  if  the  boiler  pressure  does  not  exceed  75 
pounds. 

169.  What  advantages  are  gained  by  the  use  of  mechan- 
ical stokers? 

Ans.  Regulation  of  the  supply  of  fuel  to  meet  the  de- 
mand for  steam;  also  the  opening  and  closing  of  furnace 
doors  is  avoided. 

170.  What  are  the  disadvantages  attending  the  use  of 
mechanical  stokers? 

Ans.  First,  cost  of  installation.  Second,  in  case  of  a 
sudden  demand  for  steam  the  mechanical  stoker  cannot  re- 
spond as  quickly  as  in  hand  firing.  Third,  extra  cost  for 
power  to  operate  them. 

171.  Into   how   many  classes  are  mechanical   stokers 
grouped  ? 

Ans.     Four. 

172.  Enumerate,  and  briefly  describe. 

Ans.  Class  one — An  endless  chain  of  short  grate  bars 
that  travel  horizontally  over  sprocket  wheels. 

Class  two — Grate  bars  similar  to  the  ordinary  type  hav- 
ing a  continuous  motion  up  and  down,  or  forward  and 
back,  the  bars  being  either  horizontal  or  slightly  inclined. 

Class  three — Grate  bars  steeply  inclined  and  having  a 
slow  motion. 

Class  four — Under  feed  stoker  in  which  the  coal  is  pushed 
up  onto  the  grate  by  means  of  a  revolving  screw,  or  steam 
ram. 

173.  In  what  three  forms  is  mechanical  draft  used  for 
boilers. 


Feed  Water  Heaters  29 

Ans.    First — Induced  draft. 

Second — Forced  draft,  in  which  fans  force  air  beneath 
the  grates. 
Third — A  combination  of  induced  and  forced  draft. 

174.  Is  a  good  draft  necessary  for  the  efficient  opera- 
tion of  steam  boilers? 

Ans.    It  certainly  is.     The  economical  combustion  of 
fuel  cannot  be  accomplished  without  a  good  draft. 

175.  For  what  two  purposes  are  chimneys  required? 
Ans.    First,  to  carry  of!  obnoxious  gases.     Second,  to 

create  sufficient  draft  for  the  combustion  of  the  fuel. 

176.  What  factor  governs  the  intensity  of  the  draft, 
•ndependent  of  the  dimensions  of  the  chimney? 

Ans.    The  difference  in  weight  of  the  outside  and  in- 
side columns  of  air. 

177.  What  is  the  best  shape  of  chimney? 
rAns.    Round,  with  a  straight  flue. 

178.  What  is  the  weight,  and  volume  of  air  at  a  tem- 
perature of  60°,  and  uader  average  atmospheric  pressure 
it  sea  level? 

Ans.     One  cubic  foot  weighs  536  grains,  and  13.06  cubic 
feet  weigh  one  pound. 


Care  and  Operation  of  Boilers 

179.  What  is  one  of  the  most  important  duties  of  the 
engineer  when  he  goes  on  watch  ? 

Ans.  To  ascertain  the  exact  height  of  the  water  in  his 
boilers. 

180.  Describe  the  correct  method  of  doing  this. 

Ans.  Open  the  valve  in  the  drain  pipe  of  the  water  col- 
umn, and  allow  the  water  to  blow  out  freely  for  a  few 
seconds,  then  close  the  valve  and  note  the  level  of  the  water 
when  it  settles  back  in  the  gauge  glass. 

181.  What  is  the  next  important  step  in  beginning  the 
day's  work  ? 

Ans.  To  see  that  the  fires  are  cleaned,  and  in  good  con- 
dition. 

182.  In  firing  boilers  by  hand,  what  is  the  first  and 
most  important  rule  to  be  observed? 

Ans.    Keep  a  clean  fire. 

183.  What  is  the  second  rule? 

Ans.  See  that  every  square  inch  of  grate  surface  is 
covered  with  a  good  live  fire. 

184.  Give  the  third  rule  regarding  firing  by  hand. 
Ans.    Keep  a  level  fire. 

185.  What  is  the  fourth  rule? 

Ans.  When  cleaning  the  fire,  always  clean  all  clinkers 
and  dead  ashes  away  from  the  back  end  of  the  grates  and 
the  bridge  wall. 

31 


32  Steam  Engineering 

186.  Why  should  this  be  done? 

Ans.  In  order  to  allow  a  free  passage  of  the  air  through 
the  grate  bars,  so  as  to  promote  combustion. 

187.  If  the  plant  runs  continuously,  day  and  night, 
what  is  one  of  the  important  duties  of  the  fireman  coming 
off  watch? 

Ans.  To  leave  clean  fires,  clean  ash  pits,  and  a  good 
supply  of  coal  ready  for  the  oncoming  force. 

188.  How  long  a  time  should  the  fires  be  allowed  to 
burn  before  cleaning? 

Ans.  This  depends  upon  the  quality  of  the  coal.  With 
a  coal  that  does  not  clinker  on  the  grate  bars,  an  interval 
of  7  or  8  hours  may  elapse  between  cleanings,  but  with  the 
average  soft  coal  the  fires  should  not  be  allowed  to  burn 
longer  than  4  or  5  hours  without  cleaning. 

189.  What  is  one  of  the  greatest  aids  to  good  combustion 
in  a  hand-fed  furnace? 

Ans.    A  clean  bridge  wall,  kept  as  hot  as  possible 

190.  What  precautions  should  be  observed  regarding 
the  depth  of  the  fire? 

Ans.  It  should  not  be  allowed  to  become  so  deep  and 
heavy  as  to  prevent  the  air  from  passing  up  through  it 
freely. 

191.  How  should  the  position  of  the  ash-pit  doors  be 
regulated  ? 

Ans.  With  a  clean,  light  fire,  a  slight  opening  will  be 
sufficient,  but  with  a  heavy  fire,  and  the  grates  clogged  with 
ashes,  a  larger  opening  is  necessary. 

192.  How  can  the  best  results  be  secured  in  firing 
bituminous  coal  ? 

Ans.  By  leaving  the  fire  doors  slightly  open  for  a  few 
seconds  immediately  after  throwing  in  a  fire. 


Care  and  Operation  of  Boilers  33 

193.  What  reason  is  there  for  doing  this? 

Ans.  Because  the  volatile  matter  in  the  coal  flashes  into 
flame  the  instant  it  comes  in  contact  with  the  heat  of  the 
furnace,  and  unless  there  is  sufficient  supply  of  oxygen 
present  just  then,  the  combustion  will  be  imperfect. 

194.  What  is  the  result  of  this  imperfect  combustion? 

Ans.  The  formation  of  carbonic  oxide  gas,  and  the  con- 
sequent loss  of  about  two-thirds  of  the  heat  units  contained 
in  the  coal. 

195.  How  may  this  loss  be  prevented  in  a  great  meas- 
ure? 

Ans.  By  admitting  a  sufficient  volume  of  air,  either 
through  the  fire  doors,  directly  after  throwing  in  a  fresh 
fire,  or,  better  still,  providing  air  ducts  through  the  bridge 
wall,  or  side  walls,  which  will  direct  the  air  in  on  top  of 
the  fire. 

196.  How  much  air  is  required  for  the  complete  com- 
bustion of  one  pound  of  coal? 

Ans.    By  weight  12  pounds — by  volume  150  cubic  feet. 

197.  What  precaution  is  necessary  regarding  the  tubes 
of  a  boiler  in  order  to  get  the  best  results  from  the  fuel  ? 

Ans.  The  tubes  should  be  kept  clean  and  free  from  soot 
and  scale. 

198.  Should  the  steam  jet  cleaner  be  depended  upon 
alone  for  cleaning  the  tubes? 

Ans.    No.    The  scraper  should  also  be  used. 

199.  How  should  safety  valves  be  looked  after? 

Ans.  They  should  be  ample  in  size,  never  overloaded, 
and  should  be  tested  at  least  once  a  day  to  see  that  they 
act  freely. 


34  Steam  Engineering 

200.  At  what  point  should  the  steam  gauge  pointer 
stand  when  the  pressure  is  off? 

Ans.     It  should  stand  at  zero. 

201.  What  should  be  done  in  case  of  low  water  in  a 
boiler? 

Ans.  The  fire  should  be  covered  immediately  with  ashes, 
earth,  or  if  neither  is  available  use  fresh  coal.  Draw  the 
fire  as  soon  as  it  can  be  done  without  increasing  the  heat. 

202.  Should  the  rate  of  feeding  the  water  be  increased, 
in  case  of  extremely  low  water  in  the  boiler? 

Ans.  It  should  not,  neither  should  the  engine  be  stopped 
or  the  safety  valve  lifted,  until  the  fires  are  out,  and  the 
boiler  cooled  down. 

203.  In  case  of  indications  of  cracks  or  blisters  appear- 
ng^n  the  boiler  sheets,  what  should  be  done  ? 

Ans.     There  should  be  no  delay  in  making  repairs. 

204.  What  should  be  done  with  fusible  plugs  when  used  ? 
Ans.    They  should  be  cleaned  and  carefully  scraped  on 

both  water  and  fire  sides  at  each  washing  out. 

205.  How  may  the  most  economical  results  regarding 
fuel  be  attained  with  a  steam  boiler? 

Ans.  By  keeping  the  heating  surfaces  clean,  both  inside 
and  outside,  also  careful  firing,  a  little  at  a  time,  but  keep- 
ing the  grates  covered. 

206.  Should  cold  water  ever  be  fed  into  a  boiler  when 
it  is  under  pressure? 

Ans.    Not  when  it  can  be  avoided. 

207.  How  may  foaming  usually  be  stopped? 

Ans.  By  checking  the  outflow  of  steam,  by  blowing 
down  and  pumping  up,  or  by  checking  the  draft  and  fires. 

208.  Should  air  be  allowed  to  pass  to  the  boiler  or  tubes, 
except  through  the  furnace  ? 


Care  and  Operation  of  Boilers  35 

Ans.    It  should  not,  as  it  will  cause  a  waste  of  fuel. 

209.  What  should  be  done  with  leaks  when  discovered? 
Ans.    They  should  be  repaired  as  soon  as  possible. 

210.  What  precautions  should  be  observed  when  pre- 
paring to  empty  a  boiler  for  washing  out,  or  other  pur- 
poses ? 

Ans.  Allow  it  to  cool  down  until  there  is  no  steam  pres- 
sure, and  until  the  brick  work  is  cool  also. 

211.  When  firing  up  a  boiler  what  course  should  be 
pursued  ? 

Ans.  Steam  should  be  raised  very  slowly,  and  rapid  fir- 
ing avoided. 

212.  What  bad  results  follow  too  rapid  firing  up  of  a 
boiler? 

Ans.  Straining  of  the  joints  and  seams  caused  by  un- 
equal expansion. 

213.  What  should  be  done  with  a  boiler  that  is  to 
stand  idle  for  any  length  of  time? 

Ans.  It  should  be  emptied,  and  thoroughly  dried.  In 
case  this  is  impracticable,  fill  it  full  of  water,  and  put  in 
a  quantity  of  washing  soda. 

214.  How  long  a  time  may  a  boiler  be  safely  operated 
between  dates  of  washing  out  ? 

Ans.  This  depends  upon  the  nature  of  the  feed  water. 
The  time  should  never  be  longer  than  two  weeks,  and  with 
very  bad  water,  the  boiler  should  be  washed  out  once  a 
week. 

215.  Besides  cleaning  the  boiler  inside,  what  other  very 
important  work  should  the  boiler  washer  perform  while 
inside  the  boiler? 


36  Steam  Engineering 

Ans.  He  should  closely  examine  all  braces,  stays,  and 
rivets  by  tapping  them  with  a  hammer.  Any  loose  or  de- 
fective parts  can  usually  be  detected  in  this  way. 

216.  Describe  four  ways  in  which  tube  failures  may 
occur. 

Ans.  1.  Pitting.  2.  Defective  welds.  3.  Bagging.  4. 
Scabbing  and  blistering. 

217.  How  may  a  great  saving  in  fuel  be  effected  with 
regard  to  the  feed  water  ? 

Ans.  By  heating  it  with  the  exhaust  steam  from  engines 
and  pumps  before  passing  it  to  the  boilers. 

218.  Describe  the  available  heating  surface  of  a  station- 
ary boiler,  of  either  type,  return  tubular  or  water  tube. 

Ans.  The  lower  half  of  the  shell,  and  heads,  and  the 
combined  cross  sectional  area  of  all  the  tubes. 

219.  What  should  be  the  location  of  the  water  gauge 
glass,  relative  to  the  water  level  in  the  boiler? 

Ans.  It  should  be  located  at  such  a  height  as  to  bring 
the  lower  end  of  the  glass  tube  on  a  level  with  the  danger 
point  for  low  water  in  the  boiler. 

220.  Where  should  the  lower  gauge  cock  be  located 
relative  to  the  danger  point? 

Ans.    About  three  inches  above. 

222.  Should  an  engineer  or  water  tender  depend  entirely 
upon  the  water  gauge  glasses  ? 

Ans.  He  should  not,  but  should  frequently  open  and  try 
the  gauge  cocks. 

223.  What  should  be  done  with  the  entire  water  column 
several  times  a  day? 

Ans.     It  should  be  blown  out  thoroughly. 

224.  What  should  be  done  with  the  safety  valves  in 
order  to  make  them  reliable  ? 


Care  and  Operation  of  Boilers  37 

Ans.  They  should  be  allowed  to  blow  off  at  least  twice  a 
week. 

225.  Why  is  this  necessary? 

Ans.  Because  the  valves  are  liable  to  become  corroded, 
and  stick  to  their  seats  if  not  attended  to  properly. 

226.  What  is  the  rule  for  finding  the  bursting  pressure 
of  boilers? 

Ans.  Multiply  the  tensile  strength  by  the  thickness  and 
divide  by  one-half  the  diameter  of  the  shell. 

227.  How  may  the  safe  working  pressure  of  a  boiler  be 
ascertained  ? 

Ans.     By  dividing  the  bursting  pressure  by  five. 

228.  What  is  the  rule  for  ascertaining  the  velocity  of 
flow  in  a  pump? 

Ans.  Multiply  the  number  of  strokes  per  minute  by 
length  of  stroke  in  feet.  This  will  give  piston  speed. 

229.  How  may  velocity  of  flow  in  the  discharge  pipe  of 
a  pump  be  found  ? 

Ans.  Divide  square  of  diameter  of  water  piston  by  the 
square  of  the  diameter  of  pipe,  and  multiply  by  piston  speed 
per  minute. 

230.  What  is  the  rule  for  finding  velocity  in  feet  per 
minute  required  to  discharge  a  given  quantity  of  water  in 
a  given  time  ? 

Ans.  Multiply  number  of  cubic  feet  to  be  discharged  by 
144  and  divide  by  area  of  pipe  in  inches. 

231.  When  the  volume  and  velocity  of  water  to  be  dis- 
charged are  known,  how  may  the  area  of  the  pipe  be  ascer- 
tained? 

Ans.  Multiply  volume  in  cubic  feet  by  144  and  divide 
by  velocity  in  feet  per  minute. 


38  Steam  Engineering 

232.  What  is  one  of  the  main  requisites  in  the  success- 
ful burning  of  coal  in  a  boiler  furnace? 

Ans.    A  good  draft. 

233.  What  is  a  common  cause  of  lost  economy  in  the 
operation  of  boilers? 

Ans.    Air  leaks  in  the  brick  settings. 

234.  Mention  another  source  of  loss  in  connection  with 
mechanical  stokers. 

Ans.    The  dead  area  of  grate  that  is  covered  with  a  thin 
layer  of  clinker,  and  ash. 

235.  What  is  meant  by  the  expression  "priming?" 
Ans.     Carrying  over  into  the  cylinder  of  water  in  tKc 

form  of  fine  spray  mingled  with  the  steam. 

236.  How  may  this  be  prevented  to  a  large  extent  ? 
Ans.    By  placing  a  baffle  plate  in  the  steam  space  of  the 

boiler,  directly  under  the  dome.     Steam  separators  may 
also  be  employed  for  this  purpose. 

237.  What  should  be  the  principal  object  in  view  in 
burning  coal  under  a  boiler? 

Ans.    To  transfer  as  many  as  possible  of  the  total  heat 
units  in  the  coal,  to  the  water  in  the  boiler. 


Combustion,  Heat 


238.  What  is  meant  by  the  term  combustion  as  used  in 
steam  engineering? 

Ans.  It  is  the  rapid  chemical  combination  of  oxygen 
with  the  carbon,  hydrogen  and  sulphur  in  the  fuel  with 
the  accompaniment  of  heat  and  light. 

239.  What  is  meant  by  the  symbol  C02? 

Ans.  CO 2  represents  perfect  combustion,  viz.,  the  cre- 
ation of  carbon  dioxide. 

240.  What  is  the  most  abundant  combustible  in  nature? 
Ans.     Carbon. 

241.  How  many  heat  units  are  contained  in  one  pound 
of  pure  carbon? 

Ans.     14,500. 

242.  What  is  the  heating  value  of  one  T>ound  of  hydro- 
gen gas? 

Ans.    62,000. 

243.  Give  the  composition  of  coal. 

Ans.  Fixed  carbon,  volatile  matter,  ash  and  sulphur  in 

various  proportions,  depending  upon  the  quality  of  the 
coal. 

244.  Is  sulphur  desirable  as  a  constituent  of  coal? 
Ans.  It  is  not.    The  gases  formed  from  its  combustion 

attack  the  metal  of  the  boiler,  causing  corrosion. 

245.  What  office  does  nitrogen  perform  in  combustion? 

39 


40  Steam  Engineering 

Ans.  No  useful  office.  Rather  it  is  a  detriment,  and 
in  fact  is  the  chief  source  of  loss  in  furnaces.  It  is  drawn 
in  with  the  air. 

246.    What  is  meant  by  the  term  calorific  value  of  fuel  ? 
Ans.    The  amount  of  heat  liberated  per  pound  of  fuel 
undergoing  perfect  combustion. 

248.  What  are  economizers  in  connection  with  a  boiler 
plant? 

Ans.  Coils  or  stacks  of  cast  iron  pipe  placed  within  the 
smoke  flue,  or  breeching  and  surrounded  by  the  hot  gases 
while  the  water  is  passed  through  the  pipes  on  its  way  to 
the  boilers,  thus  receiving  an  additional  amount  of  heat. 

249.  What  two  factors  are  necessary  in  order  to  attain 
economy  in  the  burning  of  coal? 

Ans.  A  constant  high  furnace  temperature  and  quick 
combustion. 

250.  Define  the  term  heat. 

Ans.  Heat  is  the  result  of  the  vibration  of  the  mole- 
cules or  atoms  composing  matter. 

251.  Upon  what  does  the  intensity  of  heat  depend? 
Ans.    Upon  the  rapidity  of  the  agitation  to  which  the 

molecules  are  subject. 

252.  What  are  the  general  effects  of  heat? 

Ans.  When  heat  is  added  to,  or  taken  away  from  a 
body  the  temperature  of  the  body  is  altered  and  its  volume 
is  varied. 

253.  What  is  absolute  zero? 

Ans.  It  is  that  degree  of  temperature  at  which,  owing 
to  the  intense  cold,  a  perfect  gas  would  disappear.  Abso- 
lute zero  is  461°  below  the  zero  of  the  Fahrenheit  ther- 
mometer. 


Combustion,  Heat  41 

254.  What  is  a  heat  unit  (B.  T.  U.)  ? 

A ns.  It  is  the  quantity  of  heat  required  to  raise  the  tem- 
perature of  one  pound  of  water  one  degree,  or  from  39° 
to  40°  F. 

255.  What  is  the  mechanical  equivalent  of  heat? 
Ans.    778  foot  pounds;  in  other  words,   778  pounds 

raised  one  foot  high. 

256.  What  is  the  specific  heat  of  any  substance? 

Ans.  The  ratio  of  the  quantity  of  heat  required  to  raise 
a  given  weight  of  that  substance  one  degree  in  tempera- 
ture, to  the  quantity  of  heat  required  to  raise  an  equal 
weight  of  water  one  degree  when  the  water  is  at  its  maxi- 
mum density,  viz.,  39.1°  F. 

257.  What  is  latent  heat? 

Ans.    Heat  given  to  a  body  and  not  warming  it. 

258.  What  is  sensible  heat? 

Ans.     Heat  given  to  a  body  and  warming  it. 

259.  Of  what  is  pure  water  composed? 

Ans.     By  volume — Hydrogen  2  parts,  oxygen  1. 

By  weight — Hydrogen  11.1  parts,  oxygen  88.9. 

260.  Is  perfectly  pure  water  desirable  for  use  in  a  steam 
boiler? 

Ans.  It  is  not,  as  it  will  cause  corrosion  and  pitting  of 
the  sheets. 

261.  What  two  ingredients  in  water  are  the  chief  causes 
of  incrustation  in  boilers? 

Ans.     The  carbonates  of  lime  and  magnesia. 

262.  What  is  steam? 

Ans.  Steam  is  the  vapor  of  water  generated  by  an  in- 
crease of  the  natural  vibrations  of  molecules  of  the  water 
through  the  application  of  heat. 


42  Steam  Engineering 

263.  What  is  saturated  steam? 

Ans.     Steam  taken  directly  from  the  boiler  to  the  engine 
without  being  superheated. 

264.  What  is  superheated  steam? 

Ans.     Steam  that  has  been  heated  to  a  higher  tempera- 
ture than  that  due  to  its  pressure. 

265.  What  should  be  done  with  all  pipes  through  which, 
live  steam  is  conducted  for  purposes  of  heating,  or  power? 

Ans.    They  should  be  well  protected  by  a  covering,  in 
order  to  prevent  loss  of  heat  by  radiation. 

266.  In  what  respect  should  steam  be  considered  in  its 
relation  to  the  engine? 

Ans.    As  a  vehicle  for  transferring  the  heat  energy  from 
the  boiler  to  the  engine. 


Evaporation  Tests 


267.  What  is  the  primary  object  of  an  evaporation  test? 
Ans.     To  ascertain  how  many  pounds  of  water  the  boilers 

are  evaporating  per  pound  of  coal  burned. 

268.  What  other  important  points  relative  to  boiler 
operation  may  be  determined  by  these  tests? 

Ans.  There  are  four.  First  —  To  determine  the  efficiency 
of  the  plant  as  an  apparatus  for  the  consumption  of  fuel, 
and  the  evaporation  of  water.  Second  —  To  determine  the 
relative  economy  of  different  varieties  of  coal,  and  other 
fuels.  Third  —  To  determine  whether  or  not  the  boilers 
are  being  operated  as  economically  as  they  might  be. 
Fourth  —  To  determine  whether  the  boilers  are  being  over 
worked. 

269.  In  what  condition  should  the  testing  apparatus 
be  maintained? 


In  first-class  condition,  ready  to  be  used  at  any 
time  for  making  a  test. 

270.  What  should  be  done  with  the  boiler,  and  all  of 
its  appurtenances  preparatory  to  making  a  test? 

Ans.    They  should  be  put  in  good  condition,  by  clean- 
ing, etc. 

271.  How  should   the  boiler  under  test  be  operated 
during  the  test? 

Ans.     At  its  full  capacity. 

272.  Where  should  the  water  level  be  at  the  beginning, 
and  close  of  the  test? 

43 


44  Steam  Engineering 

Ans.  At  the  height  ordinarily  carried,  and  its  position 
should  be  marked  by  tying  a  cord  around  one  of  the  guard 
rods  of  the  gauge  glass. 

273.  How  long  should  the  test  last? 
Ans.    About  10  hours. 

274.  How  is  the  percentage  of  moisture  in  the  steam 
determined  ? 

Ans.    By  means  of  the  calorimeter. 

275.  How  many,  and  what  kind  of  calorimeters  are 
used  for  this  purpose? 

Ans.  Two.  The  throttling  calorimeter,  and  separating 
calorimeter. 

276.  Upon  what  principle  does  the  throttling  calori- 
meter act? 

Ans.    Upon  the  principle  of  temperatures. 

277.  How  does  the  separating  calorimeter  act  ? 

Ans.  It  mechanically  separates  the  water  from  a  known 
volume  of  steam  passing  through  it. 

278.  In  what  other  manner  may  the  condition  of  steam 
regarding  its  dryness  be  approximated? 

Ans.  By  observing  its  appearance  as  it  issues  from  a 
pet  cock,  or  other  small  opening. 

279.  How  will  steam  containing  1  or  2  per  cent  of 
moisture  appear  under  such  conditions  ? 

Ans.  It  will  be  transparent  close  to  the  orifice  from 
which  it  issues. 

280.  How  is  the  chimney  draft  measured? 
Ans.  By  means  of  a  draft  gauge. 

281.  What  is  the  usual  form  of  draft  gauge? 
Ans.  A  glass  tube  bent  in  the  shape  of  the  letter  U. 

282.  Describe  the  action  of  a  draft  gauge. 


Evaporation  Tests  45 

Ans.  One  leg  of  the  U  tube  is  connected  to  the  chimney 
by  a  small  rubber  hose.  The  other  leg  is  open  to  the  at- 
mosphere. The  tube  is  partly  filled  with  water,  which 
when  there  is  no  draft  will  stand  at  the  same  height  in 
both  legs. 

283.  When  there  is  a  draft  and  the  rubber  hose  is  con- 
nected to  the  chimney  how  is  the  water  in  the  U  tube 
affected? 

Ans.  The  draft  suction  causes  the  water  in  the  leg  to 
which  the  hose  is  connected,  to  rise  while  the  level  of  the 
water  in  the  other  leg  will  be  equally  depressed. 

284.  How  is  the  intensity  of  the  draft  thus  estimated  ? 
Ans.     In  fractions  of  an  inch,  .5,  .7  or  .75  inches. 

285.  "What  is  the  object  of  flue  gas  analysis  ? 

Ans.  There  are  three.  First — To  determine  the  amount 
of  excess  air  admitted  to  the  furnace.  Second — To  de- 
termine the  character  of  the  combustion.  Third — To  as- 
certain the  heat  losses. 

286.  What  weight  of  oxygen  is  required  for  the  com- 
plete combustion  of  one  pound  of  carbon? 

Ans.     2.67  pounds.    By  volume,  32  cubic  feet. 

287.  What  gaseous  combination  is  produced  by  com- 
plete combustion? 

Ans.     Carbon  dioxide  (C02). 

288.  What  is  the  result  of  imperfect  combustion? 
Ans.    Carbon  monoxide  (CO). 

289.  How  is  the  efficiency  of  the  boiler  and  furnace 
ascertained  through  an  evaporation  test? 

Ans.  By  weighing  the  coal  consumed  and  the  water 
evaporated  during  a  certain  number  of  hours  and  dividing 
the  number  of  pounds  of  water  evaporated  by  the  number 
of  pounds  of  coal  consumed.  This  will  give  number  of 
pounds  water  evaporated  per  pound  of  coal. 


46  Steam  Engineering 

290.  What  is  meant  by  the  term  "equivalent  evapora- 
tion ?" 

Ans.  It  assumes  that  the  feed  water  enters  the  boiler 
at  a  temperature  of  212°,  and  is  evaporated  into  steam  at 
212°  and  at  atmospheric  pressure. 

291.  Why  is  this   standard  necessary  in  evaporation 
tests? 

Ans.  Because  of  the  variations  in  the  temperature  of 
the  feed  water  used  in  different  tests. 

292.  What  is  meant  by  boiler  horse-power? 

Ans.  The  evaporation  of  34%  pounds  water  from  a 
feed  temperature  of  212°  into  steam  of  the  same  tempera- 
ture; or  the  evaporation  of  30  pounds  water  from  a  feed 
temperature  of  100°  into  steam  at  70  pounds  gauge  pres- 
sure. 

293.  What  is  meant  by  the  expression  "total  heat  of 
evaporation  ?" 

Ans.  The  sum  of  the  sensible  heat  plus  the  latent  heat, 
at  boiling  point. 

294.  What  is  steam  in  its  relation  to  the  engine? 
Ans.    It  is  merely  a  vehicle  for  transferring  the  heat 

energy  from  the  boiler  to  the  engine  shaft. 


Steam  Engines 


295.  Into  what  two  general  classes  are  steam  engines 
divided. 

Ans.     Simple  and  compound. 

296.  Describe  a  simple  engine. 

Ans.  A  simple  engine  may  be  either  condensing  or  non- 
condensing,  but  its  leading  characteristic  is,  that  the  steam 
is  used  in  but  one  cylinder. 

297.  What  is  a  condensing  engine? 

Ans.  One  in  which  the  exhaust  steam  is  passed  into  an 
air-tight  vessel  in  which  a  vacuum  is  maintained,  the  ex- 
haust steam  being  there  condensed  by  coming  in  contact 
with  cold  water,  or  a  series  of  tubes  through  which  cold 
water  is  being  circulated. 

298.  Describe  a  compound  engine? 

Ans.  A  compound  engine  is  one  in  which  the  steam  is 
made  to  do  work  in  two  or  more  cylinders  before  it  is  al- 
lowed to  exhaust. 

299.  How  is  this  accomplished? 

Ans.  By  causing  the  exhaust  steam  from  the  first,  or 
high  pressure  cylinder,  to  pass  into  a  second  cylinder  of 
larger  diameter,  and,  if  the  engine  be  triple  or  quadruple 
expansion,  from  thence  into  a  third  or  fourth  cylinder, 
the  diameters  of  which  increase  in  regular  ratio. 

300.  What  is  a  non-condensing  engine? 

Ans.  One  from  which  the  steam  exhausts  directly  into 
the  atmosphere,  or  is  used  for  heating  purposes  before 
passing  out  into  the  open  air. 

47 


48  Steam  Engineering 

301.  What  disadvantage  does  a  non-condensing  engine 
constantly  labor  under? 

Ans.  The  pressure  of  the  atmosphere  amounting  to 
14.7  pounds  per  square  inch  is  constantly  in  resistance  to 
the  motion  of  the  piston. 

302.  Mention  several  other  causes  that  tend  to  increase 
the  back  pressure  upon  the  piston  of  a  non-condensing  en- 
gine. 

Ans.  The  resistance  of  bends  and  turns  in  the  exhaust 
pipe,  also  causing  the  exhaust  to  pass  through  feed  water 
heaters  or  heating  coils. 

304.  What  is  back  pressure? 

Ans.  Pressure  that  tends  to  retard  the  forward  stroke 
of  the  piston. 

305.  What  advantage  has  a  condensing  engine  over  a 
non-condensing  engine? 

Ans.  The  atmospheric  pressure  is  removed  from  in  front 
of  the  piston  to  a  degree  corresponding  to  the  height  of 
the  vacuum  that  is  maintained  in  the  condenser. 

306.  How  many  classes  of  condensers  are  there  in  gen- 
eral use? 

Ans.    Two ;  jet  condensers  and  surface  condensers. 

307.  Describe  a  jet  condenser. 

Ans.  One  in  which  the  steam  is  exhausted  into  an  air- 
tight vessel,  and  is  there  condensed  by  coming  in  contact 
with  a  jet  or  spray  of  cold  water. 

308.  How  is  this  water  removed? 

Ans.  By  means  of  the  air  pump,  which  also  maintains 
a  vacuum  in  the  condenser. 

309.  Describe  a  surface  condenser. 


Steam  Engines  49 

Ans.  It  is  an  air-tight  vessel,  either  cylindrical  or 
rectangular  in  shape,  fitted  with  a  large  number  of  brass 
or  copper  tubes,  of  small  diameter,  through  which  the  cold 
water  is  forced  by  the  circulating  pump.  A  vacuum  is 
maintained  in  the  body  of  the  condenser  by  the  air  pump, 
and  the  steam  exhausted  into  this  is  condensed  by  coming 
in  contact  with  the  cool  surface  of  the  tubes.  In  some 
cases  the  steam  passes  through  the  tubes  in  place  of  around 
them,  the  condensing  water  being  forced  into  and  through 
the  body  of  the  condenser,  and  the  vacuum  being  main- 
tained in  the  tubes. 

310.  Describe  an  injector  condenser. 

Ans.  A  condenser  in  which  the  cold  water  is  forced 
through  an  annular  enlargement  of  the  exhaust  pipe,  and 
passing  down  into  a  nozzle  which  gradually  contracts.  The 
exhaust  steam  entering  at  the  same  time  is  condensed,  the 
water  rushing  through  the  nozzle  with  a  velocity  sufficient 
to  create  a  vacuum. 

311.  About  what  quantity  of  water  is  .required  per 
horse-power  per  hour  to  condense  the  exhaust  steam  from 
an  engine? 

Ans.  About  38  to  40  gallons,  depending  upon  the  tem- 
perature of  the  condensing  water. 

312.  What  three  factors  are  necessary  to  insure  good 
economy  with  multiple  cylinder  engines? 

Ans.  First — A  high  initial  pressure.  Second — Expan- 
sion of  the  steam  to  greatest  extent  possible.  Third — Pro- 
tecting the  surfaces  of  the  cylinders  from  cooling  influences. 

313.  Describe  a  cross  compound  engine. 

Ans.  An  engine  consisting  of  two  cylinders,  each  hav- 
ing its  own  connecting  rod  and  crank,  the  cranks  being 
set  at  opopsite  ends  of  the  engine  shaft,  and  at  an  angle 


60  Steam  Engineering 

of  90°  to  each  other.    The  high  pressure  cylinder  exhausts 
into  the  low  pressure  cylinder,  usually  through  a  receiver. 

314.  Describe  a  tandem  compound  engine. 

Ans.  An  engine  having  the  two  cylinders  arranged  tan- 
dem to  each  other,  with  a  common  piston  rod,  and  connect- 
ing rod. 

315.  What  advantage  is  gained  by  this  design? 

Ans.  A  much  shorter  and  more  direct  route  for  the 
exhaust  steam  in  its  passage  from  the  high  to  the  low  pres- 
sure cylinder. 


Valves  and  Valve  Setting 

316.  What  inportant  features  in  the  operation  of  an 
engine  are  dependent  upon  a  correct  adjustment  of  the 
valves  ? 

Ans.  The  efficiency  of  the  engine,  the  economical  use 
of  steam,  and  the  regular  and  quiet  action  of  the  engine. 

317.  How  many  different  types  of  valves  are  there  in 
general  use? 

Ans.     Slide,  poppet,  rotative,  piston,  gridiron,  etc. 

318.  What  are  the  basic  principles  governing  the  ad- 
justment of  the  valves  of  an  engine,  regardless  of  the  type? 

Ans.  Admission,  cut-off,  release,  and  exhaust  closure; 
each  of  these  functions  to  occur  at  the  proper  moment  dur- 
ing one  stroke  of  the  piston. 

319.  Name  two  important  functions  of  a  valve. 
Ans.    Lap  and  lead. 

320.  What  is  the  effect  of  increasing  outside  lap  ? 
Ans.    Later  admission,  and  an  earlier  cut  off. 

321.  What  results  from  increasing  inside  lap? 

Ans.  Earlier  exhaust  closure,  and  an  increased  conpres- 
sion. 

322.  What  advantage  has  an  engine  of  the  four  valve 
type  over  a  single  valve  engine  ? 

Ans.  Each  individual  valve  may  be  adjusted  in- 
pendenfly  of  the  others. 

323.  If  a  valve  had  neither  lap  nor  lead  what  would 
be  the  position  of  the  eccentric  relative  to  the  crank? 

51 


52  Steam  Engineering 

Ans.    90°  ahead  of  the  crank. 

324.  What  is  meant  by  the  term  "angular  advance,"  and 
why  is  it  necessary  ? 

Ans.  The  distance  that  the  high  point  of  the  eccentric 
is  set  ahead  of  a  line  at  right  angles  with  the  crank.  It  ia 
necessary  in  order  to  give  the  valve  lap,  and  lead. 

325.  What  is  the  first  function  of  the  valve  at  the  com- 
mencement of  the  stroke  ? 

Ans.  Lead,  or  admission. 

326.  What  is  the  second  function? 
Ans.  Full  port  opening. 

327.  What  is  the  travel  of  a  valve  equal  to? 

Ans.  Twice  the  port  opening  plus  twice  the  outside  lap. 

328.  What  is  the  third  function  of  the  valve? 
Ans.  Cut  off. 

329.  What  is  the  fourth  function? 
Ans.  Exhaust  closure,  or  compression. 

330.  What  will  be  the  effect  if  the  valve  has  no  inside 
lap? 

Ans.  An  early  release,  and  no  compression. 

331.  What  is  meant  by  "radius  of  eccentricity  ?" 
Ans.  One  half  the  travel  of  the  valve. 

332.  What  is  an  eccentric? 

Ans.  A  mechanical  device  for  converting  rotary  into 
reciprocating  motion.  Its  center  of  revolution  is  apart 
from  its  center  of  formation. 

333.  What  is  the  "throw"  of  an  eccentric? 

Ans.  The  distance  from  the  center  of  the  eccentric  to 
the  center  of  the  shaft. 

334.  What  is  meant  by  eccentric  position? 


Valves  and  Valve  Setting  53 

Ans.    The  location  of  the  highest  point  of  the  eccentric 
relative  to  the  center  of  the  crank  pin,  expressed  in  degrees. 

335.  What  is  valve  travel? 

Ans.    The  distance  covered  by  the  valve  in  its  move- 
ment. 

336.  What  is  lap? 

Ans.    The  amount  that  the  ends  of  the  valve  project 
over  the  edges  of  the  ports  when  the  valve  is  at  mid  travel. 

337.  What  is  inside  lap? 

Ans.    The  lap  of  the  inside,  or  exhaust  edge  of  the  valve 
over  the  inside  edge  of  the  port. 

338.  What  is  outside  lap? 

Ans.    The  lap  of  the  outside  edge  of  the  valve  over  the 
outside  edge  of  the  port. 

339.  What  is  lead? 

Ans.    The  amount  that  the  port  is  open  when  the  crank 
is  on  the  dead  center. 

340.  Why  must  a  valve  have  outside  lap? 

Ans.    Because   admission   and   cut   off   are    controlled 
thereby. 

341.  Why  should  a  valve  have  inside  lap  ? 

Ans.    In  order  that  release  and  compression  may  be 
properly  controlled. 

342.  What  is  the  effect  of  decreasing  the  angular  ad- 
vance ? 

Ans.    All  the  important  functions  of  the  valve  occur 
later. 

343.  What  results  follow  from  decreasing  the  travel  of 
the  valve? 

Ans.    Less  lead,  a  later  admission  and  release,  and  an 
earlier  cut  off  and  compression. 

344.  What  is  meant  by  automatic  or  variable  cut  off? 


54  .  Steam  Engineering 

Ans.  A  system  in  which  full  boiler  pressure  is  constantly 
maintained  in  the  valve  chest,  the  speed  being  regulated  by 
the  governor  controlling  the  point  of  cut  ofi. 

345.  What  is  meant  by  fixed  cut  off? 

Ans.  When  the  point  of  cut  off  remains  the  same,  re- 
gardless of  the  load,  the  speed  being  regulated  by  throttling 
the  steam. 

346.  What  three  changes  must  be  made  in  order  to 
cause  an  earlier  cut  off  on  an  engine  that  has  a  fixed  cut  off? 

Ans.  First — Increase  the  angular  advance.  Second — 
Increase  the  outside  lap.  Third — Increase  the  inside  lap. 

347.  What  is  the  first  step  in  valve  setting? 
Ans.    To  place  the  engine  on  the  dead  center. 

348.  What  is  meant  by  the  dead  center? 

Ans.  When  the  piston  is  at  the  end  of  the  stroke,  and 
the  centers  of  the  crank  shaft,  crank  pin,  and  cross  head 
pin  are  in  line. 

349.  What  rule  should  be  observed  in  turning  an  en- 
gine to  place  it  on  the  dead  center? 

Ans.  Always  turn  it  in  the  direction  in  which  it  is  to 
run. 

350.  Why  is  this  necessary? 

Ans.  In  order  to  guard  against  errors  which  might 
result  from  lost  motion  in  the  parts. 

351.  Having  placed  the  engine  on  the  dead  center,  what 
is  to  be  done  next? 

Ans.    Adjust  the  eccentric  rod  to  the  proper  length? 

352.  What  should  be  done  with  the  valve  before  con- 
necting it  with  the  eccentric  rod  ? 

Ans.    It  should  be  placed  at  mid  travel,  and  marked.  ', 


Valves  and  Valve  Setting  55 

353.  What  is  necessary  before  the  valve  can  be  placed 
in  its  central  position? 

Ans.    The  exact  amount  of  outside  lap  must  be  known. 

354.  What  amount  of  lead  is  usually  given  to  the  valve  ? 
Ans.    From  -fa  in.  to  %  in.  depending  upon  the  size  of 

the  engine. 

355.  What  is  the  function  of  the  governor? 

Ans.    To  properly  regulate  the  speed  of  the  engine. 

356.  Explain  the  action  of  a  governor? 

Ans.  Its  action  is  based  upon  the  principle  of  the  cen- 
trifugal, and  centripetal  forces,  which  cause  the  balls  or 
weights  attached  to  the  arms,  to  fly  outward  or  inward  as 
their  speed  of  revolution  increases  or  decreases. 

357.  In  what  manner  is  this  movement  of  the  balls 
caused  to  regulate  the  speed? 

Ans.  In  the  pendulum  or  fly  ball  governor,  the  motion 
is  transferred  by  means  of  levers  and  rods  to  the  cut  ofl 
mechanism.  In  the  shaft  governor  the  changes  in  the 
position  of  the  weights  change  the  angular  advance  of  the 
eccentric,  thus  causing  an  earlier  or  later  cut  off,  according 
as  the  load  is  light,  or  heavy. 

358.  In  what  way  does  the  throttling  governor  regulate 
the  speed  of  an  engine? 

Ans.  It  controls  the  position  of  a  valve  in  the  steam 
pipe,  opening  or  closing  it  according  as  the  engine  needs 
more,  or  less  steam  to  maintain  a  regular  speed. 

359.  What  is  compression? 

Ans.  If  the  exhaust  port  is  closed  by  the  valve,  just  be- 
fore the  piston  reaches  the  end  of  stroke,  a  portion  of  the 
steam  will  be  entrapped  in  the  cylinder,  and  being  ahead 
of  the  piston  will  be  compressed. 

360.  Is  there  any  advantage  in  this? 


56  -JSteam  Engineering 

^H 

Ans.  Yes.  The  steam  thus  compressed  acts  as  a  cush- 
ion for  the  piston,  preventing  shock  or  jar  to  the  moving 
parts  on  reaching  the  end  of  the  stroke. 

361.    What  is  an  adjustable  cut  off? 

Ans.  One  in  which  the  point  of  cut  off  may  be  adjusted 
by  a  hand  wheel  attached  to  the  valve  stem  of  a  throttling 
governor. 


Definitions 


362.  What  is  absolute  pressure? 

Ans.     Pressure  reckoned  from  a  perfect  vacuum. 

363.  What  is  gauge  pressure? 

Ans.     Pressure  above  atmospheric  pressure. 

364.  What  is  initial  pressure? 

Ans.    Pressure  in  the  cylinder  at  the  beginning  of  the 
stroke. 

365.  What  is  terminal  pressure? 

Ans.     Pressure  in  the  cylinder  at  the  end  of  the  stroke. 

366.  What  is  mean  effective  pressure  (M.  E.  P.)  ? 
Ans.     The    average   pressure    acting   upon   the    piston 

throughout  the  stroke. 

367.  What  is  back  pressure? 

Ans.    Pressure  tending  to  retard  the  forward  stroke  of 
the  piston. 

368.  What  is  absolute  back  pressure? 

Ans.    Back  pressure  measured  from  a  perfect  vacuum. 

369.  What  is  the  ratio  of  expansion? 

Ans.    The  relative  volume  of  steam  in  the  cylinder  at 
point  of  release,  compared  to  volume  at  cut  off. 

370.  What  is  wire  drawing  of  steam  ? 

Ans.    Eestricted  passage  of  the  steam  caused  by  too 
small  a  steam  pipe. 

371.  What  is  condenser  pressure? 

Ans.     Pressure  existing  in  the  condenser  caused  by  the 
lack  of  vacuum. 

57 


58  Steam  Engineering 

372.  What  is  vacuum? 

Ans.    That  condition  existing  within  a  closed  vessel  from 
which  all  matter,  including  air  has  been  expelled. 

373.  What  is  absolute  zero? 
Ans.     461.2°  below  zero  Fahr. 

374.  What  is  piston  displacement? 

Ans.     The  space  swept  through  by  the  piston  in  a  single 
stroke. 

375.  What  is  piston  clearance? 

Ans.     The  distance  between  the  piston  and  cylinder  head 
at  the  end  of  the  stroke. 

376.  What  is  steam  clearance? 

Ans.     The  distance  between  the  piston  at  end  of  stroke, 
and  the  valve  face. 

377.  What  is  a  horse  power  (H.  P.)  ? 

Ans.     33,000  Ibs.  raised  one  foot  in  one  minute  of  time. 

378.  What  is  indicated  horse  power  (I.  H.  P.)  ? 

Ans.     The  horse  power  as  shown  by  the  indicator  dia- 
gram. 

379.  What  is  piston  speed? 

Ans.    The  distance  in  feet  traveled  by  the  piston  in  one 
minute. 

380.  Give  the  rule  for  figuring  the  horse  power? 

Ans.    Area  of  piston  in  square  inchesXM.  E.  P.Xpiston 
speed-f-33,000. 

381.  What  is  net  horse  power? 
Ans.     I.  H.  P.  minus  engine  friction. 

382.  Define  Boyle's  law  of  expanding  gases? 

Ans.    Pressure  at  constant  temperature  varies  inversely 
as  the  space  it  occupies. 

383.  What  is  an  adiabatic  curve? 


Definitions  59 

Ans.  The  curve  of  expanding  gas  that  loses  no  heat 
while  expanding. 

384.  What  is  an  isothermal  curve  ? 

Ans.  The  curve  of  an  expanding  gas  of  constant  tem- 
perature, but  influenced  by  moisture. 

385.  What  is  an  expansion  curve? 

Ans.  The  curve  traced  upon  the  diagram  by  the  indi- 
cator pencil. 

386.  Define  the  first  law  of  thermodynamics. 

Ans.  Heat  and  mechanical  energy  are  mutually  con- 
vertible. 

387.  What  is  power? 

Ans.     The  rate  of  doing  work. 

388.  What  is  the  unit  of  work? 

Ans.  The  foot  pound,  viz.,  the  raising  of  one  pound, 
one  foot  high. 

389.  Define  the  first  law  of  motion? 

Ans.  All  bodies  continue  either  in  a  state  of  rest,  or  of 
uniform  motion  in  a  straight  line,  unless  compelled  by  im- 
pressed forces  to  change  that  state. 

390.  What  is  work,  mechanically  considered? 
Ans.     PressureX distance  passed  throughXtime. 

391.  What  is  momentum? 
Ans.     MassX  density. 

392.  What  is  dynamics? 

Ans.    The  science  of  moving  powers. 

393.  What  is  force? 

Ans.  That  which  alters  the  motion  of  a  body,  or  puts 
in  motion  a  body  that  was  at  rest. 

394.  Define  the  maximum  theoretical  duty  of  steam? 
Ans.    Mechanical  equivalent  of  heat X  total  heat  units 

in  a  pound  of  steam? 


60  Steam  Engineering 

395.  How  may  steam  efficiency  be  expressed  ? 

Ans.     Heat  converted  into  useful  work-f-heat  expended. 

396.  How  may  engine  efficiency  be  expressed  ? 

Ans.     Heat  converted  into  useful  work-r-total  heat  re- 
ceived in  the  steam. 

397.  How  may  efficiency  of  the  plant  be  expressed? 
Ans.    Heat  converted  into  useful  work-f-calorific  or  heat 

value  of  the  fuel. 

398.  What  is  horse  power  constant  ? 

Ans.     The  power  the  engine  would  develop  with  one 
pound  M.  E.  P. 

399.  What  is  meant  by  steam  consumption  per  H.  P. 
per  hour? 

Ans.     Weight  in  pounds  of  steam  used-^H.  P.  developed. 

400.  What  are  ordinates  as  applied  to  indicator  dia- 
grams? 

Ans.    Parallel  lines  drawn  at  equal  distances  across  the 
face  of  the  diagram,  perpendicular  to  atmospheric  line. 


Indicator 


401.  What  two  important  points  are  gained  by  the  use 
of  the  indicator? 

Ans.  First — It  shows  the  average  pressure  upon  the 
piston  throughout  the  stroke.  Second — It  shows  the  action 
of  the  valve  or  valves  in  admission,  cut  ofi  and  release  of 
the  steam. 

402.  What  is  the  first  principle  of  the  indicator? 

Ans.  Pressure  of  the  steam  in  the  engine  cylinder  dur- 
ing an  entire  revolution,  against  a  small  piston  in  the  cylin- 
der of  the  indicator. 

403.  What  resistance  is  in  front  of  the  indicator  piston  ? 
Ans.    A  spiral  spring  of  known  tension. 

404.  What  is  the  second  principle  of  the  indicator? 
Ans.    By  means  of  a  multiplying  mechanism  of  levers, 

the  stroke  of  the  indicator  piston  is  communicated  to  a 
pencil  moving  in  a  straight  line. 

405.  What  is  the  third  principle  of  the  indicator? 
Ans.     By  means  of  a  reducing  mechanism  and  cord,  the 

motion  of  the  engine  piston  during  an  entire  revolution  is 
imparted  to  a  small  rotating  drum,  to  which  is  attached  a 
piece  of  blank  paper. 

406.  How  is  a  diagram  obtained? 

Ans.  The  pencil  is  held  against  the  paper  and  thus  traces 
a  diagram  of  the  action  of  the  steam  within  the  engine 
cylinder. 

407.  What  is  the  atmospheric  line? 

61 


62  Steam  Engineering 

Ans.  A  line  drawn  by  the  indicator  pencil  before  com- 
munication is  established  between  engine  cylinder  and  indi- 
cator cylinder. 

408.  Where  should  a  diagram  from  a  non-condensing 
engine  appear  relative  to  the  atmospheric  line? 

Ans.     It  should  appear  above  the  atmospheric  line. 

409.  Where  should  the  diagram  from  a  condensing  en- 
gine appear? 

Ans.  Partly  above,  and  partly  below  the  atmospheric 
line. 

410.  What  is  the  best  reducing  motion  to  use? 
Ans.  The  reducing  wheel. 

411.  How  is  the  indicator  attached  to  the  engine  cylin- 
der? 

Ans.  By  means  of  half-inch  pipe  tapped  into  the  side  of 
the  cylinder  near  the  ends. 

412.  How  are  the  springs  numbered? 

Ans.  They  are  made  for  various  pressures,  and  num- 
bered accordingly. 

413.  What  is  a  good  rule  to  follow  in  selecting  a  spring? 
Ans.     Select  one  numbered  one-half  as  high  as  the  boiler 

pressure,  which  will  give  a  diagram  about  two  inches  high. 

414.  What  data  should  be  noted  upon  the  diagrams 
when  they  are  taken? 

Ans.  Boiler  pressure;  time  when  taken,  and  which  end 
of  cylinder,  head,  or  crank. 

415.  What  pressure  must  always  be  deducted  from  the 
mean  forward  pressure   (M.  F.  P.)   in  calculations  for 
power  ? 

Ans.    The  back  pressure. 

416.  What  bad  effects  follow  unequal  cut  off? 


Indicator  63 

Ans.     The  engine  will  not  develop  the  power  that  it  is 
capable  of — uneven  strains  will  be  set  up. 

417.  What  is  a  convenient  size  for  a  diagram? 
Ans.     I1/?  or  2  inches  high,  and  2  or  21/*?  inches  long. 

418.  What  precaution  regarding  the  pipe  connections 
of  the  indicator  should  always  be  observed  before  taking 
diagrams  ? 

Ans.     They  should  be  thoroughly  blown  out,  and  cleaned 
of  all  dirt. 

419.  How  is  the  ratio  of  expansion  found? 

Ans.     Divide  absolute  initial  pressure  by  absolute  ter- 
minal pressure. 

420.  Name  a  very  important  factor  in  the  calculation 
of  steam  consumption  of  an  engine. 

Ans.     The  clearance  space. 

421.  What  is  one  of  the  first  requisites  in  power  calcu- 
lations ? 

Ans.    To  ascertain  the  M.  E.  P. 

422.  How  is  this  done?  ,  : 

Ans.    In  several  ways,  for  instance  by  means  of  ordinates, 
or  it  may  be  obtained  by  the  use  of  the  Planimeter. 


Lubrication 


423.  What  is  one  of  the  most  important  problems  con- 
nected with  engine  operation? 

Ans.     The  proper  lubrication  of  the  bearings. 

424.  What  is  friction? 

Ans.  The  resistance  caused  by  the  motion  of  a  body  in 
contact  with  another  body  that  does  not  partake  of  its 
motion. 

425.  What  is  the  first  law  of  friction? 

Ans.  Friction  varies  in  proportion  to  the  pressure  on 
the  surfaces  in  contact. 

426.  Define  the  second  law  of  friction. 

Ans.  Friction  is  independent  of  the  areas  of  surface  in 
contact. 

427.  What  is  the  third  law  of  friction? 

Ans.  Friction  increases  with  the  roughness  of  the  sur- 
faces, and  decreases  as  the -surf  aces  become  smoother. 

428.  What  is  the  fourth  law  of  friction? 

Ans.     Friction  is  greatest  at  the  beginning  of  motion. 

429.  Give  the  fifth  law  of  friction? 

Ans.  Friction  is  greater  between  soft  bodies  than  it  is 
between  hard  bodies. 

430.  When,  and  by  whom  were  these  laws  first  formu- 
lated? 

Ans.  In  1831-33  by  Gen.  Arthur  Morin,  a  French  en- 
gineer. 

431.  What  is  the  tendency  of  friction  with  machinery 
in  operation? 

65 


66  Steam  Engineering 

Ans.  It  tends  to  cause  the  parts  to  adhere  to  each  other. 

432.  How  may  this  friction  be  largely  obviated  ? 
Ans.  By  proper  lubrication  of  the  rubbing  surfaces. 

433.  Does  friction  serve  any  good  purpose  ? 

Ans.  Yes,  for  instance  the  friction  of  the  belt  in  con- 
tact with  the  rim  of  the  pulley,  also  the  friction  of  the 
driving  wheels  of  a  locomotive. 

434.  How  many  kinds  of  friction  are  there  in  connec- 
tion with  machinery  in  operation  ? 

Ans.  Two,  viz.,  the  friction  of  solids,  and  the  friction 
of  liquids. 

435.  What  is  meant  by  the  term  co-efficient  of  friction? 
Ans.     The  ratio  of  the  power  required  to  move  a  body, 

and  the  pressure  on  that  body. 

436.  What  should  be  the  object  sought  in  the  design 
of  engine  bearings? 

Ans.     To  obtain  as  large  a  rubbing  surface  as  possible. 

437.  Mention  some  of  the  qualities  that  a  good  lubri- 
cating oil  should  possess. 

Ans.  It  should  have  a  good  "body" — must  not  dry  or 
"gum ;"  must  not  be  easily  thinned  by  heat,  or  thickened  by 
cold.  Must  be  free  from  all  gritty  substances. 

438.  What  is  the  proper  kind  of  oil  to  use  on  a  bearing 
that  has  started  to  heat? 

Ans.  Cylinder  oil,  owing  to  its  high  fire  test. 

439.  Is  graphite,  or  plumbago  a  good  lubricant? 
Ans.  It  is  in  many  cases. 

440.  What  is  the  essential  function  of  graphite? 
Ans.  It  is  an  auxiliary,  or  accessory  lubricant. 

441.  Mention  some  of  the  points  that  govern  interior 
lubrication  of  engine  parts. 


Lubrication  67 

Ans.  The  conditions  of  the  surfaces ;  the  steam  pressure ; 
the  amount  of  moisture  in  the  steam ;  piston  speed ;  weight, 
and  fit  of  moving  parts,  etc. 

4:4:2.     What  properties  should  a  good  cylinder  oil  possess  ? 

Ans.  It  must  be  of  high  flash  test;  must  have  good 
viscosity,  or  body  when  in  contact  with  hot  surfaces. 

443.  Upon  what  does  the  successful  lubrication  of  an 
engine  largely  depend? 

Ans.  Upon  the  character  of  the  lubricating  appliances 
used. 

444.  What  system   of   lubrication   for  cylinders,   and 
valves  is  most  largely  used? 

Ans.     The  hydrostatic,  or  sight-feed  type  of  lubricator. 

445.  What  other  system  has  come  into  extensive  use  in 
late  years? 

Ans.    The  force  feed,  or  mechanically  operated  oil  pump. 


The  Steam  Turbine 

446.  Explain  the  chief  points  of  difference  between 
the  action  of  the  reciprocating  steam  engine,  and  the  steam 
turbine. 

Ans.  The  piston  of  the  reciprocating  engine  is  driven 
back  and  forth  by  the  static  expansive  force  of  the  steam; 
while  in  the  steam  turbine,  not  only  is  this  static  expansive 
force  made  to  do  work,  but  the  velocity  of  the  steam  in  ex- 
panding from  a  high,  to  a  low  pressure  is  also  utilized  in 
turning  the  rotor  of  the  turbine. 

447.  What  other  important  factors  enter  into  the  opera- 
tion of  a  steam  turbine? 

Ans.    The  principles  of  reaction  and  impulse. 

448.  Name  several  of  the  more  important  advantages 
that  the  turbine  has  over  the  reciprocating  engine. 

Ans.  First,  highly  superheated  steam  of  a  high  initial 
pressure  may  be  used  in  the  turbine.  Second,  a  larger 
proportion  of  the  heat  in  the  steam  may  be  converted  into 
work  with  the  turbine.  Third,  there  is  much  less  friction 
with  the  turbine. 

449.  What  is  the  most  economical  method  of  disposing 
of  the  exhaust  steam  from  a  turbine? 

Ans.    By  allowing  it  to  pass  into  a  condenser. 

450.  Will  the  turbine  expand  the  steam  to  as  low  a 
pressure  as  the  reciprocating  engine  will? 

Ans.    Yes,  and  even  lower. 

69 


70  Steam  Engineering 

451.  What  type  of  condensing  apparatus  is  necessary 
with  the  steam  turbine. 

Ans.  The  same  kind  that  is  used  on  reciprocating  en- 
gines. 

452.  How  low  will  a  well  regulated  turbine  allow  the 
steam  to  expand  ? 

Ans.  To  within  one  inch  of  the  vacuum  existing  in 
the  condenser. 

453.  What  is  the  theoretical  velocity  of  steam  under 
100  Ibs.  pressure  if  allowed  to  discharge  into  a  vacuum  of 
28  inches? 

Ans.     3860  feet  per  second. 

454.  How  many  ft.  Ibs.  of  energy  would  one  cubic  ft. 
of  steam  thus  exert? 

Ans.     59,900  ft.  Ibs. 

455.  What  is  the  ratio  of  bucket  speed  to  jet  speed  for 
impulse  wheels. 

Ans.    Bucket  speed  equals  one-half  of  jet  speed. 

456.  What  should  be  the  ratio  between  bucket  speed 
and  jet  speed,  for  reaction  wheels. 

Ans.     1  to  1.    That  is,  the  two  speeds  should  be  equal. 

457.  What  should  be  the  form  or  curvature  of  the 
blades,  or  buckets? 

Ans.  They  should  be  of  such  form  as  will  permit  expan- 
sion of  the  steam  with  the  least  amount  of  friction,  or  eddy 
currents. 

458.  How  are  the  stuffing  boxes  of  steam  turbines  usu- 
ally kept  cooled? 

Ans.    By  means  of  water  applied  in  various  ways. 

459.  How  is  the  speed  of  steam  turbines  usually  regu- 
lated? 


Steam  Turbines  71 

Ans.     By  simple  throttling. 

460.  What  are  the  ideal  conditions  under  which  a  tur- 
bine should  work? 

Ans.  A  full  initial  pressure,  and  all  cross  sections  of 
steam  passages  to  be  suitable  to  the  power  required. 

461.  Of  what  type  is  the  Westinghouse-Parsons  turbine  ? 
Ans.     It  is  both  an  impulse  and  reaction  turbine. 

462.  How  are  the  clearances  between  the  blades  pre- 
served in  this  turbine? 

Ans.     By  means  of  balancing  pistons  on  the  shaft. 

463.  What  is  the  usual  velocity  of  the  steam  in  the 
Westinghouse-Parsons  turbine  ? 

Ans.     600  ft.  per  second. 

464.  How  does  the  efficiency  of  steam  turbines  compare 
with  that  of  reciprocating  engines? 

Ans.     It  is  generally  higher. 

465.  How  is  the  heat  energy  in  the  steam  imparted  to 
the  wheels  of  the  Curtis  turbine? 

Ans.     Both  by  impulse  and  reaction. 

466.  Describe  the  method  of  admission  in  the  Curtis 
turbine. 

Ans.  The  steam  is  admitted  through"  expanding  nozzles 
in  which  nearly  all  of  the  expansive  force  of  the  steam  is 
transformed  into  the  force  of  velocity.  The  steam  is  caused 
to  pass  through  one,  two,  or  more  stages  of  moving  ele- 
ments, each  stage  having  its  own  set  of  expanding  nozzles, 
each  succeeding  set  of  nozzles  being  greater  in  number  and 
of  larger  area  than  the  preceding  set. 

467.  What  is  the  ratio  of  expansion  in  these  nozzles? 


72  Steam  Engineering 

Ans.  The  ratio  of  expansion  within  these  nozzles  de- 
pends upon  the  number  of  stages,  as,  for  instance,  in  a  two- 
stage  machine,  the  steam  enters  the  initial  set  of  nozzles  at 
boiler  pressure,  say  180  Ibs.  It  leaves  these  nozzles  and 
enters  the  first  set  of  moving  blades  at  a  pressure  of  about 
15  Ibs. 

468.  In  a  four-stage  machine,  with  180  Ibs  initial  pres- 
sure, what  would  be  the  pressures  at  the  different  stages  ? 

Ans.  First  stage,  50  Ibs.;  second  stage,  5  Ibs.;  third 
stage,  partial  vacuum,  and  fourth  stage,  condenser  vacuum. 

469.  How  are  the  revolving  parts  of  the  Curtis  turbine 
supported  ? 

Ans.  Upon  a  vertical  shaft,  which  in  turn  is  supported 
by,  and  runs  upon  a  step  bearing  at  the  bottom. 

470.  How  is  this  step  bearing  lubricated? 

Ans.  Oil  is  forced  under  pressure  by  a  steam  or  elec- 
trically driven  pump,  the  oil  passing  up  from  beneath. 

471.  How  is  the  speed  of  the  Curtis  turbine  regulated  ? 
Ans.    By  varying  the  number  of  nozzles  in  flow. 

472.  How  are  the  clearances  adjusted  in  the  Curtis 
turbine  ? 

Ans.    By  means  of  the  large  step  screw  at  the  bottom. 

473.  How  is  the  shaft  packed  to  prevent  steam  leakage? 
Ans.    With  carbon  blocks  made  into  rings  fitting  the 

shaft. 

474.  What  type  of  turbine  is  the  De  Laval? 
Ans.  It  is  purely  an  impulse  wheel. 

475.  What  is  the  speed  of  the  wheel? 

Ans.     From  10,000  to  30,000  revolutions  per  minute. 

476.  How  is  the  heat  energy  in  the  steam  utilized  in 
the  De  Laval  turbine? 

Ans.     In  the  production  of  velocity. 


Steam  Turbines  73 

477.  What  is  the  velocity  of  the  steam  as  it  issues  from 
the  expanding  nozzles  and  impinges  against  the  buckets  ? 

Ans.  About  4,000  ft.  per  second. 

478.  What  is  the  usual  peripheral  speed  of  the  wheel? 
Ans.  1,200  to  1,300  feet  per  second. 

479.  Of  what  type  is  the  Allis-Chalmers  steam  turbine  ? 
Ans.  It  is  essentially  of  the  Parsons  type. 

480.  How  are  the  clearances  between  the  revolving  and 
stationary  blades  preserved? 

Ans.     By  a  thrust  bearing. 

481.  What  kind   of  bearings  has   the   Allis-Chalmers 
turbine  ? 

Ans.     Self-adjusting  ball  and  socket  bearings. 

482.  What  is  the  first  move  in  preparing  to  start  a 
steam  turbine? 

Ans.  Open  the  throttle  slightly  and  allow  a  small  vol- 
ume of  steam  to  flow  through  in  order  to  warm  the  tur- 
bine. 

483.  What  should  be  done  next? 
Ans.     Start  the  auxiliary  oil  pump. 

484.  What  are  the  principal  precautions  to  be  observed 
when  starting  a  steam  turbine? 

Ans.  To  see  that  the  turbine  is  properly  warmed,  also 
to  be  certain  that  the  oil  is  circulating  freely  through  the 
bearings. 

485.  What  type  of  turbine  is  the  Hamilton-Holzwarth 
steam  turbine? 

Ans.     It  is  an  impulse  turbine. 

486.  Describe  in  brief  its  construction? 

Ans.  There  are  no  balancing  pistons  in  this  machine, 
the  axial  thrust  of  the  shaft  being  taken  up  by  a  thrust 
ball-bearing.  The  interior  of  the  cylinder  is  divided  into 


74  Steam  Engineering 

a  series  of  stages  by  stationary  discs  which  are  set  in 
grooves  in  the  cylinder  and  are  bored  in  the  center  to  allow 
the  shaft,  or  rather  the  hubs  of  the  running  wheels  that  are 
keyed  to  the  shaft,  to  revolve  in  this  bore. 

487.  In  what  respect  does  this  turbine  resemble  a  com- 
pound reciprocating  engine? 

A  ns.  The  steam  is  first  admitted  to  the  high  pressure 
casing,  and  from  there  it  passes  into  the  low  pressure  cas- 
ing, which  is  larger  in  diameter. 

488.  Describe  the  action  of  the  steam  upon  the  blades? 
Ans.    The  expansion  of  the  steam  takes  place  entirely 

within  the  stationary  blades,  which  also  change  the  direc- 
tion of  its  flow,  distributing  it  to  the  running  vanes. 

489.  What  additional  function  do  the  stationary  vanes 
perform  ? 

Ans.  They  take  the  back  pressure,  thus  acting  as  balanc- 
ing pistons. 

490.  What  type  of  governor  has  this  turbine? 
Ans.     The  spring  and  weight  type. 

491.  How  are  the  bearings  lubricated? 

Ans.  The  oil  is  forced  into  the  bearings  under  pressure 
by  an  oil  pump. 

492.  Of  what  type  is  the  Rateau  steam  turbine? 

Ans.  It  is  an  impulse  turbine  having  wheels  of  thin 
plates,  slightly  conical. 

493.  How  is  the  rotor  balanced? 

Ans.  The  same  pressure  exists  on  both  sides  of  each 
rotating  wheel. 

494.  Does  the  steam  act  by  velocity  or  pressure? 
Ans.     By  velocity  in  this  case. 

495.  What  are  the  essential  features  of  the  Reidler- 
Stumpf  steam  turbine? 


Steam  Turbines  75 

A ns.  The  peculiar  form  of  bucket,  and  the  parallel 
return  of  the  steam. 

496.  What  is  meant  by  parallel  return  of  the  steam? 
Ans.     The  steam   enters  the  buckets  through  nozzles, 

and  is  deflected  through  an  angle  of  180  degrees,  thus  leav- 
ing the  rotating  buckets  in  a  direction  parallel  to  that  of 
its  entrance. 

497.  Describe  the  action  of  the  steam  within  the  Reid- 
ler-Stumpf  turbine. 

Ans.  Instead  of  escaping  after  having  once  passed 
through  the  buckets,  it  is  caught  by  the  guides  or  stationary 
buckets  and  returned  to  the  wheel;  this  process  being  re- 
peated again,  and  again  until  all  of  the  energy  in  the  steam 
has  been  made  to  do  work. 

498.  How  many  types  of  this  turbine  are  there? 

Ans.     Two,  viz.:  The  single  flow,  and  the  double  flow. 

499.  How  is  the  highest  efficiency  obtained  in  the  oper- 
ation of  the  steam  turbine  ? 

Ans.  By  allowing  the  exhaust  steam  to  pass  into  a 
condenser. 

500.  Is  it  possible  to  maintain  as  high  vacuum  with 
the  turbine  as  with  a  reciprocating  engine? 

Ans.  Experience  demonstrates  that  a  higher  vacuum 
may  be  maintained  in  the  condenser  of  a  turbine  than  is 
possible  with  reciprocating  engines. 

501.  What  kind  of  condensing  apparatus  may  be  used 
with  steam  turbines? 

Ans.     Any  one  of  the  modern  improved  types. 

502.  What  is  required  in  order  to  maintain  a  high 
vacuum  in  any  type  of  condenser? 

Ans.    That  all  entrained  air  be  excluded. 

503.  How  may  this  be  accomplished? 


76  Steam  Engineering 

Ans.     By  means  of  a  dry  air  pump. 

504.  In  what  manner  does  the  dry  air  pump  differ  from 
an  ordinary  air  pump? 

Ans.     The  dry  air  pump  handles  no  water,  and  the  clear- 
ances are  made  as  small  as  possible. 

505.  To  what  extent  does  the  steam  turbine  expand  its 
working  steam? 

Ans.     To  within  one  inch  of  the  vacuum  existing  within 
the  condenser. 

506.  Is  the  steam  turbine  adapted  to  the  use  of  super- 
heated steam? 

Ans.     It  is.    Highly  superheated  steam  may  be  used,  and 
a  high  vacuum  maintained. 

507.  Is  the  water  of  condensation  from  turbines  desir- 
able for  boiler  feed  ? 

Ans.     It  is,  for  the  reason  that  it  contains  no  lubricating 
oil,  and  is  a  comparatively  pure  water. 


The  Gas  Engine 


508.  In  what  respect  does  the  gas  engine  differ  from  the 
steam  engine  structurally? 

Ans.  It  is  a  much  more  ponderous  machine  than  a  steam 
engine  of  equal  output,  and  usually  requires  a  much  heavier 
crank  shaft. 

509.  Why  should  this  be? 

Ans.  Because  the  ordinary  four-stroke-cycle,  gas  engine 
has  only  one  working  stroke  in  four,  and  requires  four 
limes  as  much  cylinder  area  for  a  given  amount  of  work, 
as  would  a  steam  engine  for  the  same  work. 

510.  Define  the  difference  between  a  single  acting  four 
stroke  cycle  and  a  double  acting  or  two  stroke  cycle  gas 
engine  in  their  operation. 

Ans.  In  the  four  stroke  engine  two  revolutions  of  the 
crank  are  required  for  one  cycle.  In  the  cfouble  acting  or 
two  stroke,  the  cycle  is  completed  in  one  revolution  of  the 
crank. 

511.  Why  are  gas  engine  crank  shafts  made  larger  in 
proportion  than  those  of  steam  engines? 

Ans.  In  order  that  they  may  withstand  the  increased 
torsional  strains. 

512.  What  causes  the  pressure  behind  the  piston  of  the 
gas  engine? 

Ans.  The  combustion  within  the  cylinder  of  a  charge 
of  gas  and  air  properly  mixed  to  form  an  explosive,  and 
admitted  at  the  proper  moment. 

513.  When  is  this  proper  moment? 

77 


78  Steam  Engineering 

Ans.  When  the  piston  is  at  the  end  of  its  instroke 
ready  to  start  outward. 

514.  Define  the  stages  of  a  four  cycle  engine. 

Ans.  First,  induction;  during  an  out  stroke  of  the 
piston,  air  and  gas  are  drawn  into  the  cylinder  in  the 
proper  proportions.  Second,  compression;  on  the  return 
stroke  the  piston  compresses  this  combustible  mixture 
into  the  clearance  space.  Third,  explosion ;  ignition  of  the 
compressed  charge  causes  a  rapid  rise  of  pressure  and  sub- 
sequent expansion  of  products.  Fourth,  expulsion;  the 
expanded  gases  are  expelled  by  the  returning  piston. 

515.  Define  the  stages  of  a  two  cycle  gas  engine. 

Ans.  First,  compression  of  the  charge.  Second,  igni- 
tion, explosion,  and  expansion,  and  at  the  end  of  the 
stroke  the  expanded  products  are  expelled,  and  the  cylinder 
filled  by  another  charge  of  air  and  gas  under  pressure. 

516.  How  many  compression  chambers  are  needed  for 
the  two  cycle  gas  engine? 

Ans.  Two;  for  the  reason  that  this  type  of  gas  engine 
requires  two  cylinders,  either  side  by  side,  or  tandem,  and 
the  charge  of  gas  and  air  is  being  received  in  one  cylinder, 
while  the  previous  charge  in  the  other  cylinder  is  being 
compressed  preparatory  for  explosion. 

517.  How  is  the  usefulness  of  the  gas  engine  as  a  prime 
mover  made  apparent? 

Ans.  By  the  fact  that  a  suitable  power  gas  may  now  be 
produced  from  almost  any  kind  of  commercial  fuel. 

518.  What  are  the  relative  volumes  of  gas  and  air  re- 
quired for  combustion  in  a  gas  engine? 

Ans.  This  depends  upon  the  kind  of  gas.  Natural  gas 
requires  10  to  12  cu.  ft.  of  air  per  cubic  feet  of  gas,  while 
producer  gas  requires  equal  volumes  of  gas  and  air. 


The  Gas  Engine  79 

519.  Is  blast  furnace  gas  suitable  for  fuel  gas? 

Ans.  Yes,  because  it  is  slow  burning,  thus  permitting 
high  compression. 

520.  To  what  pressures  may  it  be  compressed  ? 
Ans.     160  to  200  Ibs.  per  sq.  in. 

521.  Is  the^e  as  much  heat  in  a  given  volume  of  blast 
furnace  gas  as  in  the  same  volume  of  natural  gas  ? 

Ans.     No,  there  is  about  40  per  cent  less. 

522.  How  is  the  charge  of  gas  and  air  drawn  into  the 
cylinder  of  a  gas  engine? 

Ans.     By  the  suction  of  the  piston. 

523.  What   precaution  should   be   observed   regarding 
the  admission  of  the  air  and  gas? 

Ans.  The  air  should  be  pure  and  free  from  dust,  and 
the  gas  should  not  contain  tarry  matters  if  it  can  be 
avoided. 

524.  How  are  the  induction  valves  usually  set? 

Ans.  So  that  the  first  portion  of  the  charge  is  air  only, 
then  air  and  gas,  and  finally  air  with  a  small  quantity  of 
gas. 

525.  How  is  the  air  valve  controlling  the  entry  of  the 
entire  charge  adjusted? 

Ans.  It  is  set  to  open  well  in  advance  of  the  inner  dead 
center  of  the  engine,  and  is  kept  from  closing  until  after 
the  outer  dead  center. 

526.  Why  is  this  valve  so  set? 

Ans.  In  order  that  the  full  effect  of  the  momentum 
imparted  to  entering  gases  at  the  highest  rate  of  piston 
speed  may  be  utilized. 

527.  Upon  what  does  the  allowable  compression  pres- 
sure depend? 


80  Steam  Engineering 

Ans.  Upon  the  relative  proportions  of  hydro-carbon 
gases,  and  hydrogen  contained  in  the  mixture. 

528.  What  per  cent  of  hydrogen  is  considered  within 
the  limits  of  safety? 

Ans.     Not  over  7  per  cent. 

529.  What  are  the  usual  compression  pressures  carried 
with  blast  furnace  gas? 

Ans.     200  Ibs.  per  sq.  in. 

530.  What  pressure  may  be  safely  carried  when  pro- 
ducer gas  is  used? 

Ans.     From  150  to  200  Ibs.  per  sq.  in. 

531.  If  illuminating  gas  is  used,  what  is  the  maximum 
safe  pressure? 

Ans.     120  Ibs.  per  sq.  in. 

532.  How  is  the  cylinder  cooled  and  cleaned? 

Ans.  By  the  injection  of  water  or  cold  air  through 
the  clearance  spaces,  and  valve  ports  during  the  charging 
stroke,  or  by  pressure  during  compression. 

533.  What  other  methods  are  available  for  cooling  the 
cylinder  and  piston  rod  ? 

Ans.  By  means  of  a  water  jacket  that  surrounds  the 
cylinder.  The  piston  rod  may  be  hollow  and  water  cir- 
culated through  it. 

534.  How  is  the  charge  of  gas  and  air  ignited? 

Ans.  Formerly  by  hot  tubes  of  porcelain  or  hecnum, 
which  are  still  used  to  some  extent,  but  at  the  present  day 
electrical  ignition  devices  are  used  principally. 

535.  What  kind  of  electrical  devices  are  used  for  this 
purpose  ? 

Ans.  Primary  batteries,  storage  batteries,  and  magneto 
machines,  or  the  current  may  be  taken  from  the  lighting, 
or  power  circuit. 


The  Gas  Engine  8l 

536.  How  many  types  of  primary  batteries  are  in  com- 
mon use? 

Ans.     Two — Dry  and  wet  batteries. 

537.  What  are  the  elements  commonly  used  in  the  wet 
battery? 

Ans.  Carbon  and  zinc  immersed  in  a  jar  or  cell  con- 
taining a  solution  of  sal  ammoniac,  or  sulphate  of  copper. 

538.  Describe  the  copper  oxide  battery. 

Ans.  It  consists  of  a  plate  of  copper  oxide,  and  a  zinc 
plate,  both  being  immersed  in  a  solution  of  caustic  potash. 

539.  What  is  the  usual  voltage  of  these  cells? 
Ans.    From  1  to  2  volts  per  cell. 

540.  Describe  in  brief  the  construction  of  the  storage 
cell? 

Ans.  It  consists  of  gridded  frames  of  lead,  part  of  which 
are  filled  with  red  lead  for  the  positive  plates,  and  those  for 
the  negative  plates  are  filled  with  litharge,  all  being  im- 
mersed in  a  solution  of  6  parts  of  water  to  1  part  of  sul- 
phuric acid. 

541.  How  is  a  dry  battery  made? 

Ans.  A  round  zinc  case  forms  one  of  the  elements,  and 
a  piece  of  carbon  in  the  center  of  the  case  forms  the  other 
element. 

542.  Are  there  any  other  ingredients? 

Ans.  Yes — A  mixture  of  powdered  manganese,  carbon, 
and  flour  is  packed  around  the  carbon,  while  the  rest  of  the 
can  is  filled  with  a  plaster  mixture  of  oxide  of  zinc  and 
flour,  and  the  whole  is  soaked  in  a  solution  of  sal  ammo- 
niac and  zinc  chloride. 

543.  In  what  manner  does  the  electric  current  ignite 
the  charge- of  gas  in  the  cylinder? 


82  Steam  Engineering 

Ans.  By  means  of  the  jump  spark  caused  by  alternately 
making  and  breaking  the  circuit. 

544.  What  is  one  of  the  most  important  features  con- 
nected with  ignition? 

Ans.     To  see  that  ignition  occurs  at  the  proper  moment. 

545.  At  what  point  in  the  stroke  of  the  piston  should 
ignition  occur? 

Ans.  This  depends  upon  the  quality  of  the  gas  used. 
With  the  maximum  allowable  percentage  of  hydrogen,  igni- 
tion should  not  occur  until  after  the  piston  has  passed  the 
inner  dead  center.  Otherwise  the  result  will  be  violent 
shocks,  and  strains  upon  the  working  parts. 

546.  Do  high  initial  explosions  create  the  most  powerful 
efforts  behind  the  piston? 

Ans.    They  do  not. 

547.  What  are  the  usual  terminal  pressures  for  gas 
engines  ? 

Ans.    25  to  30  Ibs.  above  atmospheric  pressure. 

548.  How  is  the  horse  power  of  a  gas  engine  calculated  ? 

Ans.  Usually  from  the  same  formula  used  in  connec- 
tion with  the  steam  engine,  and  the  computation  is  based 
upon  the  mean  effective  pressure  developed  at  each  ex- 
plosion. 

549.  What  percentage  of  the  total  calorific  value  of 
the  coal  is  usually  converted  into  useful  work  with  the 
steam  engine? 

Ans.     From  5  to  10  per  cent. 

550.  What  percentage  of  the  energy  contained  in  the 
fuel  is  it  possible  to  utilize  with  a  modern  gas-driven  unit? 

Ans.     From  16  to  20  per  cent. 

551.  How  many  type  of  apparatus  are  in  use  for  the 
production  of  gag  for  power? 


TKe  Gas  Engine  83 

Ans.  Three:  the  suction  producer,  the  steam  pressure 
producer,  and  the  induced  down  draft  producer. 

552.  What  kind  of  fuel  must  be  used  in  the  suction, 
and  steam  pressure  producers? 

Ans.     Coke,  or  anthracite  coal. 

553.  What  kind  of  fuel  is  the  induced  down  draft  pro- 
ducer adapted  for? 

Ans.     Bituminous  coal. 

554.  How  may  gas  engine  efficiency  be  expressed? 
Ans.     In  terms  of  heat  value. 

555.  Is  there  any  difference  of  importance  between  a 
gas  engine,  and  a  gasoline  or  oil  engine  ? 

Ans.  None  of  any  importance.  A  gas  engine  may  be 
easily  converted  into  a  gasoline  engine,  or  vice  versa. 

556.  Wherein  lies  the  principal  difference  between  the 
two  kinds  of  engines? 

Ans.  In  the  gas  engine  proper  the  gas  is  supplied  to 
the  cylinder  by  the  producer.  In  the  gasoline  engine  the 
gas  is  generated  within  the  cylinder,  from  a  charge  of 
gasoline. 

557.  How  may  the  action  of  the  gas  within  the  cylinder 
of  a  gas  engine  be  ascertained  ? 

Ans.     By  means  of  diagrams  taken  with  an  indicator. 

558.  Is  there  any  difference  between  a  steam  engine  in- 
dicator, and  an  indicator  adapted  for  gas  engines  ? 

Ans.  None  in  principle.  The  gas  engine  indicator  is 
made  somewhat  stronger  owing  to  the  high  pressures  used. 


UNIVERSITY 

OF 


Air  Compressors 


559.  What  is  one  of  the  results  of  compressing  air? 
Ans.     The  development  of  heat. 

560.  What  amount  of  work  is  lost  by  the  development 
and  dissipation  of  this  heat? 

Ans.  The  work  represented  by  the  mechanical  equiva- 
lent of  the  heat  developed. 

561.  Mention  another  cause  of  more  or  less  lost  work 
in  air  compression? 

Ans.  Friction  of  the  air  in  the  pipes  through  which  it 
is  conveyed. 

562.  By  what  two  methods  is  air  compression  generally 
accomplished  ? 

Ans.  Isothermal,  by  which  the  heat  of  compression  is 
carried  away  as  fast  as  developed ;  and  adi^abatic,  by  which 
no  heat  is  removed  from  the  air. 

563.  Which  of  the  two  is  the  ideal  method  of  com- 
pression ? 

Ans.  The  isothermal. 

564.  Is  it  possible  of  attainment? 
Ans.  Not  entirely. 

565.  What  may  be  said  of  the  adiabatic  method? 
Ans.  It  is  one  which  should  be  avoided  as  much  as 

possible. 

566.  What  are  the  actual  results  secured  in  the  best 
compressors  ? 

Ans.  They  are  intermediate  between  the  two  meth- 
ods just  mentioned,  but  nearer  to  the  second  method. 

85 


86  Steam  Engineering 

567.  Upon  what  does  the  efficiency  of  an  air  compres- 
sor depend  principally? 

Ans.    Upon  the  effectiveness  of  the  cooling  devices. 

568.  How  many  practical  methods   of   removing  the 
heat  of  compression  are  there? 

Ans.     Two — jacket  cooling,  and  intercooling. 

569.  Is  jacket  cooling  of  the  compressor-cylinder  ef- 
fective ? 

Ans.  Not  entirely,  except  with  single-stage  compres- 
sion. 

570.  What  is  an  intercooler? 

Ans.  It  is  a  cooling  device  interposed  between  the 
cylinders  of  a  compound  or  multi-stage  machine,  through 
which  the  air  passes  on  its  way  from  one  cylinder  to 
the  next  one. 

571.  Describe  the  process  of  compression  by  the  multi- 
stage method? 

Ans.  A  multi-stage  compressor  has  two  or  more  cylin- 
ders, the  intake  or  low  pressure  cylinder  being  the  lar- 
gest in  diameter,  and  in  which  the  air  is  first  compressed 
to  a  low  pressure,  and  then  passed  on  into  the  next  cylin- 
der which  is  of  smaller  diameter,  where  the  air  is  com- 
pressed to  a  still  higher  pressure,  and  so  on  in  increasing 
ratio. 

572.  How  should  the  cylinder  ratios  be  proportioned? 
Ans.     So  that  the  M.  E.  P.  and  the  final  temperature 

are  equal  in  all  the  cylinders. 

573.  Describe  the  construction  of  an  intercooler? 
Ans.     It  usually  consists  of  a  nest  of  tubes  through 

which  cold  water  circulates,  and  between  which  the  stream 
of  air  passes. 


Air  Compressors  87 

574.  Which  method,  single-stage,  or  multi-stage,  ap- 
proaches nearest  to  the  theoretical  ideal? 

Ans.     The  multi-stage,  with  intercoolers. 

575.  Mention  another  point  in  favor  of  multi-stage 
compression  ? 

Ans.  It  permits  a  higher  piston  speed,  thus  econo- 
mizing in  steam. 

576.  What  is  one  of  the  greatest  difficulties  encoun- 
tered in  air  power  transmission? 

Ans.  Freezing  of  the  moisture  in,  the  air,  either  in 
the  pipe  line,  or  at  the  exhaust  ports  of  the  air  motors. 

577.  How  may  this  condition  be  avoided  to  a  large 
extent? 

Ans.  By  the  proper  cooling  of  the  air  during  compres- 
sion, which  will  precipitate  the  moisture,  which  may  then 
be  withdrawn  by  drain  pipes. 

578.  What  would  be  the  resultant  temperature  of  air 
compressed  from  atmospheric  pressure,  and  60°  Fahr.,  to 
a  final  pressure  of  100  Ibs.,  provided  there  was  no  cooling 
device  ? 

Ans.     484°  Fahr. 

579.  What  effect  would  this  have  upon  the  cylinder 
lubricant  ? 

Ans.     It  would  be  burned,  and  be  useless. 

580.  What   would   be   the   temperature    of   the   same 
volume  of  air  if  compressed  in  the  first,  or  intake  cylinder 
of  a  multi-stage  machine  to  a  pressure  of  25  Ibs.  ? 

Ans.     233°  Fahr. 

581.  If  passed  through  an  intercooler  on  its  way  to 
cylinder  No.  2,  what  would  its  temperature  be? 

Ans.  It  would  be  brought  back  to  its  original  tem- 
perature of  60°  Fahr.  and  enter  the  second  cylinder  under 
a  pressure  of  25  Ibs. 


88  Steam  Engineering 

582.  What  would  the  temperature  of  the  same  air  be 
if  compressed  in  cylinder  No.  2  from  25  Ibs.  to  100  Ibs. 
pressure  ? 

Ans.  It  would  be  but  little  in  excess  of  that  attained 
in  the  first  cylinder,  viz.,  233°  Fahr. 

583.  Why  would  it  not  attain  the  temperature  stated 
in  the  answer  to  question  578,  viz.,  484°  Fahr.? 

Ans.  Because  the  heat  of  compression  is  a  function  of 
the  number  of  compressions,  and  practically  independent 
of  the  initial  pressure. 

584.  Why  is  air  compression  at  high  altitudes  more  ex- 
pensive than  at  sea  level? 

Ans.  Because  the  capacity  of  the  compressor  decreases 
in  a  greater  ratio  than  does  the  power  necessary  to  com- 
press. 

585.  At  an  elevation  of  10,000   ft.   above  sea  level, 
what  is  the  increase  in  expense  ? 

Ans.     Over  20  per  cent. 

586.  What  should  be  the  first  care  in  the  installation 
of  an  air  compressor? 

Ans.    To  provide  a  suitable  foundation. 

587.  What  precautions  should  be  observed  in  the  pip- 
ing? 

Ans.  First,  there  should  be  as  few  L's  as  possible,  and 
second,  all  pipes  should  be  thoroughly  cleaned  before  start- 
ing the  compressor;  third,  allowance  should  be  made  for 
expansion. 

588.  What  is  the  function  of  the  unloader  on  the  In- 
gersoll-Eand  air  compressor? 

Ans.  To  take  the  load  off  the  air  piston  when  the  pres- 
sure reaches  the  desired  point. 

589.  What  is  the  function  of  the  regulator? 


Air  Compressors  89 

Ans.    To  regulate  the  supply  of  steam  to  the  steam 
end  of  the  compressor. 

590.  What  type  of  air  inlet  valves  is  this  compressor 
equipped  with? 

Ans.    Piston  inlet  valves. 

591.  Describe  the  action  of  these  valves? 

Ans.    The  air  enters  and  passes  through  the  piston,  thus 
tending  to  keep  it  cooled. 

592.  What  is  the  function  of  the  Mason  pump  gov- 
ernor, with  which  some  air  compressors  are  equipped? 

Ans.    To  maintain  a  constant  speed  regardless  of  the 
load. 

593.  What  kind  of  inlet  valves  is  the  Dallett  air  com- 
pressor fitted  with? 

Ans.    Either   mechanically   operated    valves,    or   auto- 
matic poppet  valves,  as  desired. 

594.  With  what  type  of  valves  are  the  Allis-Chalmers 
air  compressors  usually  equipped? 

Ans.    Rotary  valves  for  the  inlet,  and  single-beat  poppet 
valves  for  the  discharge. 

595.  How  are  the  inlet  valves  operated? 

Ans.    By  an  eccentric  on  the  main  shaft,  and  a  wrist 
plate. 

596.  What  other  type  of  valve-gear  are  some  of  these 
compressors  equipped  with? 

Ans.     Both  inlet,  and  discharge  valves  are  actuated  by 
independent  eccentrics  on  the  main  shaft. 


Refrigeration 


597.  Of  what  does  the  process  of  refrigeration  consist? 
Ans.     In  the  abstraction  of  heat  from  a  substance. 

598.  Describe  a  freezing  mixture  that  will  give  a  tem- 
perature of  67  degrees  below  zero. 

Ans.  A  mixture  of  one  pound  of  calcium  chloride,  and 
0.7  Ibs.  of  snow. 

599.  Upon  what  are  the  theory,  and  practice  of  mechan- 
ical refrigeration  based? 

Ans.     Upon  the  two  first  laws  of  thermo-dynamics. 

600.  What  is  the  first  of  these  laws? 

Ans.  Mechanical  energy  and  heat  are  mutually  con- 
vertible. 

601.  Define  the  second  law. 

Ans.  An  external  agent  is  necessary  tp  complete  or 
bring  about  this  transformation. 

602.  Is  heat  generated  by  compression,  or  by  any  other 
means  ? 

Ans.  It  is  not  generated  but  developed,  because  there 
is  a  fixed  amount  of  heat  in  the  universe  which  can  neither 
be  increased  nor  diminished. 

603.  "What  is  the  result  of  compressing  one  pound  of 
air  at  70  degrees  temperature  and  at  atmospheric  pressure, 
to  one  half  its  original  volume  ? 

Ans.  An  increase  in  its  static  pressure,  also  an  increase 
in  its  temperature. 

604.  In  order  that  the  higher  pressure  may  be  main- 
tained, as  the  temperature  is  reduced,  what  is  necessary? 

91 


92  Steam  Engineering 

Ans.  A  small  additional  quantity  of  air  will  have  to  be 
forced  into  the  compressor  cylinder. 

605.  If  the  pound  of  compressed  air  be  allowed  to  ex- 
pand in  a  cylinder  what  will  be  the  result  ? 

Ans.  A  portion  of  the  heat  developed  by  compression 
will  be  given  up. 

606.  What  can  be  said  of  the  mechanical  work  done 
by  this  air  in  its  expansion? 

Ans.  In  amount  it  is  exactly  the  same  as  that  done  upon 
it  during  its  compression. 

607.  How  is  the  temperature  of  a  body  or  substance 
reduced  ? 

Ans.  »By  transferring  more  or  less  of  the  heat  con- 
tained in  the  body  to  some  other  substance  or  body. 

608.  What  work  is  demanded  of  a  refrigerating  ma- 
chine? 

Ans.  To  extract  heat  from  a  body,  and  by  the  expendi- 
ture of  mechanical  energy  to  sufficiently  raise  the  temper- 
ature of  this  heat  to  admit  of  its  being  carried  away  by  a 
suitable  external  agent,  usually  water. 

609.  How  may  a  refrigerating  machine  be  defined,  and 
what  is  its  main  function? 

Ans.  As  a  heat  pump,  its  main  function  being  the 
abstraction  of  heat  from  the  body  to  be  cooled,  and  trans- 
ferring that  heat  to  a  cooling  agent. 

610.  How  may  the  various  devices  for  refrigeration  and 
ice  making  be  classified? 

Ans.    Under  five  principal  heads. 

611.  Explain   the   action   of   apparatus   belonging  to 
class  one. 

Ans.  Heat  is  abstracted  from  the  body  to  be  cooled, 
by  the  dissolution  or  liquefaction  of  a  solid,  as  for  instance 
the  cooling  of  water  with  ice. 


Refrigeration  93 

612.  Describe  the  vacuum  system? 

Ans.  The  abstraction  of  heat  is  effected  by  the  evapora- 
tion of  a  portion  of  the  liquid  to  be  cooled,  the  process 
being  assisted  by  an  air  pump. 

613.  How  is  refrigeration  effected  in  machines  belong- 
ing to  the  third  class? 

Ans.  By  the  evaporation  of  a  separate  refrigerating 
agent,  which  is  subsequently  restored  to  its  original  physi- 
cal condition  by  mechanical  compression  and  cooling. 

614.  Describe  the  fourth  or  absorption  system. 

Ans.  Heat  is  abstracted  by  the  evaporation  of  a  sepa- 
rate refrigerating  agent,  under  the  direct  action  of  heat, 
which  agent  again  enters  in  solution  with  a  liquid. 

615.  Describe  the  action  of  machines  belonging  to  the 
fifth  class,  known  as  cold  air  machines  ? 

Ans.  Air,  or  other  gas  is  first  compressed,  then  cooled, 
and  afterwards  permitted  to  expand  while  doing  work. 

616.  What  two  systems  have  come  into  general  use  in 
the  United  States? 

Ans.  The  ammonia  compression  system,  and  the  am- 
monia absorption  system. 

617.  What  are  the  three  distinct  stages  in  the  com- 
pression system? 

Ans.     Compression,  condensation,  and  expansion. 

618.  What  is  the  refrigerating  agent  or  medium  used 
in  the  compression  system? 

Ans.     Anhydrous  ammonia. 

619.  Of  what  does  ammonia  consist,  and  what  is  its 
chemical  formula? 

Ans.  One  part  of  nitrogen,  and  three  parts  of  hydro- 
gen. Its  chemical  formula  is  NH3. 

620.  Under  what  two  conditions  may  gaseous  ammonia 
be  liquefied? 


94  Steam  Engineering 

Ans.  At  a  pressure  of  128  Ibs.  per  sq.  in.,  and  a  tem- 
perature of  70°  Fahr.,  or  a  pressure  of  150  Ibs,  and  a  tem- 
perature of  77°  Fahr.  It  may  also  be  liquefied  by  cold  if 
its  temperature  be  reduced  to  85.5°  Fahr.  below  zero. 

621.  To   what   pressure   is  gaseous   ammonia  usually 
compressed  ? 

Ans.    From  125  to  175  Ibs.  per  sq.  in. 

622.  Of  what  does  a  compression  plant  consist? 

Ans.  Of  a  high  pressure  system  made  up  of  a  condens- 
ing coil  surrounded  by  cooling  water,  and  a  low  pressure 
system  consisting  of  an  evaporating  coil  surrounde4  by 
brine,  or  open  to  the  room  to  be  cooled. 

623.  What  takes  place  during  compression? 

Ans.  The  latent  heat  of  the  vapor  is  converted  into 
active,  or  sensible  heat. 

624.  How  is  the  vapor  condensed,  or  liquefied? 

Ans.  It  is  forced  into  and  through  the  condenser  coils 
which  are  submerged  in  a  body  of  cold  water,  or  over  which 
cold  water  is  flowing,  and  the  sensible  heat  developed  dur- 
ing compression  is  thus  transferred  to  the  cooling  water. 

625.  How  are  the  refrigerating  qualities  of  the  am- 
monia in  its  liquefied  state  utilized? 

Ans.  It  is  allowed  to  pass  in  small  quantities  from  the 
condenser  into  pipe  coils  placed  in  the  rooms  to  be  cooled, 
when  it  again  expands  into  a  vapor,  and  takes  up  an 
amount  of  heat  exactly  equivalent  to  that  given  up  during 
condensation. 

626.  After  being  expanded  into  vapor,  what  becomes 
of  it? 

Ans.  It  is  drawn  back  into  the  compressor,  again  com- 
pressed, condensed,  and  expanded,  the  cycle  of  operations 
being  repeated  indefinitely. 


Refrigeration  95 

627.  How  many,  and  what  are  the  systems  of  refrigera- 
tion by  compression? 

Ans.     Two — the  wet  system,  and  the  dry. 

628.  Describe  the  theory  of  the  wet  system. 

Ans.  The  ammonia  vapor  is  cooled  by  the  injection 
into  the  compressor  C3rlmder  of  a  small  quantity  of  liquid 
ammonia  at  the  beginning  of  each  stroke,  and  it  is  carried 
from  the  cooling  room  back  to  the  compressor  in  a  sat- 
urated state.  It  is  thus  kept  in  contact  with  a  small  por- 
tion of  its  originating  fluid,  and  is  kept  comparatively  cool. 

629.  Upon  what  does  the  pressure  of  steam  in  a  boiler 
depend  ? 

Ans.  Upon  its  temperature,  which  is  always  the  same  as 
that  of  the  water  in  the  boiler. 

630.  What  are  the  relations  of  temperature  and  pres- 
sure in  the  case  of  steam  while  in  contact  with  the  originat- 
ing water? 

Ans.    They  are  interdependent. 

631.  What  is  the  result  if  the  steam  is  superheated? 
Ans.    It  may  still  be  of  the  same  pressure,  but  its  tem- 
perature will  be  higher. 

632.  What  results  from  the  compression  of  a  dry  gas 
without  cooling? 

Ans  Its  temperature  may  be  much  higher  than  that 
corresponding  to  its  pressure. 

633.  What  does  the  Adiabatic  curve  as  traced  by  the 
indicator  represent? 

Ans.  The  compression,  or  expansion  of  a  gas  without 
loss  or  gain  of  heat. 

634.  Describe  in  brief  the  construction  of  the  cylinder 
heads,  and  valves  in  the  Linde  ice  machine. 


96  Steam  Engineering 

Ans.  The  piston  and  cylinder  heads  are  spherical,  and 
of  the  same  radius,  and  the  valve  discs  conform  to  this 
radius. 

635.  What  is  the  clearance  between  piston  and  cylin- 
der head  ? 

Ans     One  thirty-second  of  an  inch. 

636.  How  is  the  piston  lubricated? 

Ans.  In  a  large  measure  by  the  moisture  in  the  am- 
monia vapor. 

637.  In  the  De  La  Vergne  refrigerating  machine  how 
is  the  heated  gas  cooled? 

Ans.  By  passing  it  through  coils  of  pipe  surrounded 
by  running  water. 

638.  How  many  valves  has  the  Triumph  ice  machine? 
Ans.    Five,   three   suction   valves,   and   two   discharge 

valves. 

639.  What  advantage  is  said  to  be  gained  by  the  use 
of  the  third  suction  valve? 

Ans.  That  it  tends  to  increase  the  economy  of  the  ma- 
chine. 

640.  Describe  the  construction  of  a  double  pipe  am- 
monia condenser. 

Ans.  It  consists  of  two  series  of  coils,  one  within  the 
other. 

641.  How  many  methods  are  there  of  utilizing  refrig- 
eration ? 

Ans.  Two;  the  brine  system,  and  the  direct  expansion 
system. 

642.  Describe  in  brief  the  brine  system. 

Ans.  The  coils  of  pipe  in  which  the  ammonia  is  ex- 
panded are  submerged  in  a  solution  of  salt,  or  calcium 
chloride.  This  brine  after  being  reduced  to  a  low  tempera- 


Refrigeration  97 

ture  is  pumped  through  coils  of  pipe  in  the  rooms  to  be 
cooled. 

643.  Describe  the  direct  expansion  system. 

Ans.  The  expansion  coils  are  placed  in  the  rooms  to  be 
cooled,  and  the  cooling  is  effected  directly  by  the  expansion 
of  the  ammonia. 

644.  Which  one  of  the  two  systems  is  the  most  efficient? 
Ans.     The  direct  expansion  system. 

645.  Mention  a  few  of  the  advantages  that  this  system 
has  over  the  brine  system. 

Ans.  First — All  intermediate  agencies  are  dispensed 
with.  Second — The  whole  plant  is  much  simpler.  Third 
— A  larger  expansion  surface. 

646.  By  what  two  systems  is  ice  made  or  manufactured? 
Ans.     The  can  system  and  the  plate  system. 

647.  Mention  other  refrigerating  agents  besides  am- 
monia that  may  be  used  in  the  compression  system  ? 

Ans.  Ether,  methyl-chloride,  sulphurous  acid,  and  car- 
bonic acid. 

648.  How  is  refrigeration  effected  in  the  absorption 
system  ? 

Ans.  By  the  continuous  distillation  of  ammoniacal 
liquor. 

649.  What    advantage    appertains    to    the    absorption, 
system  ? 

Ans.  The  bulk  of  the  heat  required  for  the  work  is 
applied  direct  without  being  transformed  into  mechanical 
power. 

650.  What  pressure  is  usually  maintained  in  the  gen- 
erator ? 

Ans.     150  Ibs.  per  sq.  in. 

651.  Mention  the  more  important  features  of  the  ab- 
sorption machine? 


98  Steam  Engineering 

Ans.  The  expansion  valve,  the  absorber,  and  the 
strength  of  the  liquor. 

652.  Upon  what  does   the   efficiency   of  the  machine 
mostly  depend? 

Ans.  Upon  the  condition  of  the  absorber.  If  it  is  cool 
and  free  from  air,  or  poor  gas,  better  results  will  be 
realized. 

653.  What  should  be  done  if  one  side  of  the  absorber 
should  get  warmer  than  the  other  ? 

Ans.  The  spray  valve  should  be  turned  down  slightly, 
say  one-eighth  of  a  turn. 

654.  Mention  one  of  the  troubles  in  the  operation  of 
this  system. 

Ans.     A  filling  up  of  the  coils  with  scale  and  dirt. 

655.  What  is  the  remedy  in  such  cases? 

Ans.  Stop  the  machine  once  a  week,  drain  the  coils,  and 
blow  them  out  with  compressed  air. 

656.  How  is  anhydrous  ammonia  formed? 

Ans.  By  condensing  ammonia  gas  to  a  liquid,  and 
applying  pressure. 

657.  Under  atmospheric  pressure,  what  is  the  boiling 
point  of  anhydrous  ammonia? 

Ans.     28.5  degrees  delow  zero  Fahr. 

658.  What  is  the  specific  gravity  of  liquid  ammonia 
compared  with  water? 

Ans.  At  32°  Fahr.  it  is  about  %  that  of  water,  or 
0.6364. 

659.  What  is  its  latent  heat  of  evaporation  ? 

Ans.    At  32  degrees  temperature  it  is  560  thermal  units. 

660.  If  evaporated  at  32°  Fahr.  and  atmospheric  pres- 
Bure,  how  much  space  will  one  pound  occupy? 

Ans.    Twenty-one  cubic  feet. 


Elevators — Electric  and  Hydraulic 

661.  What  are  the  essential  parts  of  the  Otis  traction 
elevator  ? 

Ans.  A  traction  motor  driving  sheave,  and  a  pair  of 
electrically  released  brake  shoes. 

662.  What  type  of  electric  motor  is  used  in  the  Otis 
traction  elevator? 

Ans.    A  slow  speed  shunt-wound  motor. 

663.  What  is  the  principal  function  of  the  armature 
shaft  besides  carrying  the  armature? 

Ans.    To  support  the  load. 

664.  How,  then,  is  the  drum,  or  sheave  driven? 
Ans.     By  means  of  projecting  arms  from  the  armature, 

that  engage  with  similar  arms  projecting  from  the  d.rum. 

665.  Describe  the  system  of  safety  devices  with  which 
this  elevator  is  equipped  ? 

Ans.  There  are  two  groups  of  switches  located,  respec- 
tively at  top  and  bottom  of  the  shaft,  each  switch  in  series 
being  opened  one  after  the  other  by  the  car  as  it  passes. 
This  retards  the  speed  and  finally  brings  the  car  to  stop, 
applying  the  brake,  independent  of  the  operator  in  car. 

666.  Are  there  any  other  safeties  besides  this  ? 

Ans.  Yes — speed  governors,  wedge  clamps  for  gripping 
the  guides,  and  potential  switches. 

667.  Describe  in  general  terms  the  construction  of  the 
Otis  geared  traction  elevator? 

Ans.  A  multi-grooved  driving  sheave  around  which  th'e 
cable  works.  The  sheave  is  mounted  upon  a  shaft  driven 

99 


100  Steam  Engineering 

by  geared  wheels  actuated  by  a  right  and  left  hand  worm 
cut  on  the  armature  shaft. 

668.  What  advantage  is  gained  by  the  use  of  the  double 
screw,  or  worm  ? 

Ans.     The  elimination  of  all  end  thrust. 

669.  With  what  kind  of  brake  is  this  machine  equipped? 
Ans.    A  mechanically  applied,  and  electrically  released 

brake. 

670.  What  type  of  motor  is  used? 

Ans.     Compound-wound — speed  800  R.  P.  M. 

671.  When  is  the  series  field  of  this  motor  used? 
Ans.     Only  at  starting. 

673.    Why? 

Ans.    To  obtain  a  highly  saturated  field  in  the  shortest 
possible  time. 

673.  How  is  a  gradual  slowing  down  of  speed  of  car 
obtained  with  this  elevator? 

Ans.    By  throwing  a  low  resistance  field  across  the  ar- 
mature, thus  providing  a  dynamic  brake  action. 

674.  What  kind  of  current  is  used  for  operating  elec- 
tric elevators? 

Ans.    Either  alternating,  or  direct  current. 

675.  How  is  the  transmission  of  current  to  the  motor 
of  an  electric  elevator  controlled? 

Ans.    By  means  of  an  electric  magnet  controller  op- 
erated through  the  switch  in  the  car. 

676.  How  may  considerable  power  be  wasted  in  the 
operation  of  electric  elevators? 

Ans.    By  careless  handling — making  unnecessary  stops 
and  starts,  or  too  sudden  stops  or  starts. 

677.  Briefly,  of  what  does  the  mechanism  of  a  hydraulic 
elevator  consist? 


Elevators — Electric  and  Hydraulic  101 

Ans.  A  cylinder  and  piston  with  one  or  more  rods  con- 
nected to  a  crosshead  which  carries  the  sheaves  over  which 
run  the  lifting  cables  from  which  the  car  is  suspended. 

678.  What  moves  the  piston? 

Ans.  Water  under  pressure  admitted  by  means  of  suit- 
able valves  causes  the  piston  to  move  from  one  end  of  the 
cylinder  to  the  other,  and  back  again. 

679.  How  is  this  motion  transmitted  to  the  elevator 
car? 

Ans.  By  means  of  the  sheaves  mounted  on  the  cross- 
head  which  carry  the  lifting  cables. 

680.  In  what  position  is  the  cylinder  placed  ? 

Ans.    Either  vertical  alongside  the  hatchway,  or  hori- 
zontal in  the  basement  of  the  building. 

681.  How  are  the  valves  of  a  hydraulic  elevator  op- 
erated ? 

Ans.  In  some  cases  by  a  hand  rope  passing  through 
the  car  and  over  small  sheaves  at  the  top  and  bottom  of 
the  hatchway,  and  connected  with  the  main  valve  in  the 
basement.  By  pulling  this  rope  down  the  valve  is  opened, 
and  the  car  will  ascend,  while  pulling  the  rope  up  will 
cause  the  car  to  descend. 

682.  What  safety  devices  are  attached  to  this  type  of 
elevator  ? 

Ans.  Two  balls  are  attached  to  the  hand  rope,  one  near 
the  bottom,  and  the  other  near  the  top.  These  balls  come 
in  contact  with  the  top,  or  bottom  of  the  car,  according 
as  it  is  going  up  or  coming  down,  and  being  carried  along 
they,  of  course  move  the  cable,  thus  actuating  the  valve, 
bringing  the  car  to  a  stop. 

683.  Is  this  device  safe,  and  automatic? 
Ans.    It  is. 


102  Steam  Engineering 

684.  Mention   another   safety   device   connected   with 
hydraulic  elevators. 

Ans.  Safety  clamps  under  the  control  of  a  speed  limit 
centrifugal  governor  which  causes  the  clamps  to  grip  the 
guides  and  thus  hold  the  car. 

685.  How  is  this  safety  governor  operated? 

Ans.  By  means  of  a  small  cable  connected  with  the  car 
and  moving  with  it,  which  passes  over  the  sheave  pulley 
of  the  governor. 

686.  Why  are  some  elevator  pistons  fitted  with  two  pis- 
ton rods? 

Ans.  To  prevent  the  piston,  and  crosshead  from  turn- 
ing or  twisting,  and  also  to  strengthen  the  construction. 

687.  What  other  methods  are  used  for  manipulating 
the  water  valve,  besides  the  one  already  described? 

Ans.  Running  ropes,  and  standing  ropes,  either  of 
which  may  be  operated  by  means  of  a  lever,  or  wheel  in 
the  car. 

688.  Do  these  devices  directly  operate  the  main  valve? 
Ans.     No.    They  operate  a  small  valve  called  the  pilot 

valve. 

689.  What  is  the  function  of  the  pilot  valve? 

Ans.  When  opened  it  admits  the  pressure  water  to  a 
small  cylinder  with  piston  connected  to  the  main  valve 
stem.  This  actuates  the  main  valve,  which  in  turn,  by  its 
movement,  closes  the  pilot  valve. 

690.  Upon  what  does  the  amount  of  opening  given  the 
pilot  valve,  and  consequently  the  main  valve  depend? 

Ans.  Upon  the  distance  the  lever  in  the  car  is  moved 
from  central  position. 

691.  What  is  meant  by  central  position  of  lever? 


Elevators — Electric  and  Hydraulic  103 

Ans.  That  position  in  which  there  is  no  flow  of  water 
either  into  or  out  of  the  cylinder,  and  the  car  is  moving 
only  by  its  momentum. 

692.  What  is  the  result  of  moving  the  lever  too  quickly 
to  central  position  when  the  car  is  moving  at  a  high 
rate  of  speed? 

Ans.  The  motion  of  the  car  will  be  arrested  with  a 
sudden  jerk. 

693.  How  many  kinds  of  horizontal  hydraulic  elevators 
are  in  use  ? 

Ans.  Two.  One  is  the  pushing,  and  the  other  the 
pulling  type. 

694.  Describe  the  action  of  the  pushing  type? 

Ans.  The  car  being  at  the  bottom,  the  pressure  water 
is  admitted  behind  the  piston  which  then  moves,  pushing 
the  crosshead  and  cable  sheave  and  lifting  the  car. 

695.  Describe  the  action  of  the  pulling  type? 
Ans.     It  is  the  opposite  of  that  just  described. 

696.  Is  there  much  difference  in  the  valve  mechanism 
of  the  horizontal,  and  vertical  types  of  hydraulic  elevators  ? 

Ans.     Very  little  except  a  few  minor  details. 

697.  What  is  meant  by  a  double-deck  machine? 

Ans.  Where  the  floor  space  is  restricted  two,  and  some- 
times three  or  four  machines  are  mounted  one  above  the 
other. 

698.  What  water  pressure  is  usually  carried  in  operat- 
ing the  types  of  hydraulic  elevators  that  have  hitherto 
been  described? 

Ans.  Pressures  not  exceeding  200  Ibs.,  the  average  being 
150  Ibs.  per  square  inch. 

699.  Are  any  higher  pressures  than  this  being  used  for 
operating  hydraulic  elevators? 

Ans.     Yes.    Pressures  of  700  to  800  Ibs.  and  higher. 


104:  Steam  Engineering 

700.  Why  are  such  high  pressures  used? 

Ans.  Owing  to  increased  height  of  buildings,  and  the 
demand  for  high  car  speed. 

701.  What  advantage,  other  than  high  speed,  is  gained 
by  the  use  of  high  pressure  elevators? 

Ans.  A  reduction  in  the  size  of  the  valve  mechanism, 
piston  areas  and  piping. 

702.  Mention   another   advantage  in   connection  with 
the  high  pressure  system? 

Ans.  A  reduction  in  the  loss  by  friction  of  the  water 
passing  through  the  pipes,  owing  to  reduced  areas. 

703.  What  is  the  percentage  of  loss  due  to  this  cause? 
Ans.     In  low  pressure   machines   from   10  to   30   per 

cent,  and  in  high  pressure  machines  from  5  to  6  per  cent. 

704.  Describe  in  general  terms  the  construction  of  the 
cylinder  and  piston  of  a  high  pressure  machine. 

Ans.  The  cylinder  area  is  reduced  to  about  one-eighth 
that  of  the  low  pressure  type,  and  the  piston  is  a  solid 
plunger. 

705.  How  is  the  pressure  maintained? 

Ans.  The  pump  forces  water  into  the  lower  end  of  the 
accumulator,  an  air-tight  tank,  which  is  also  weighted. 
From  the  accumulator  a  pipe  runs  to  the  main  valve. 

706.  Describe  in  general  terms  the  construction  and 
operation  of  the  direct-acting  plunger  elevator. 

Ans.  A  cylinder  is  set  vertically  in  the  ground  under 
the  center  of  the  car,  and  the  length  of  it  is  slightly 
greater  than  the  travel  of  the  car.  In  this  cylinder  is  a 
plunger  of  the  same  length,  which  carries  the  car.  Water 
under  pressure  is  forced  into  the  cylinder  and  thus  lifts 
the  car,  and  allowed  to  run  out  at  the  top  when  the  car 
descends.  The  cylinder  is  about  two  inches  larger  in  dia- 
meter than  the  plunger,  and  is  always  full  of  water. 


Elevators — Electric  and  Hydraulic  105 

707.  What  is  the  usual  diameter  of  the  plunger? 
Ans.     6!/2  to  7  inches. 

708.  How  is  it  constructed? 

Ans.  Of  lengths  of  highly  polished  steel  pipe,  joined 
together  with  an  internal  sleeve,  and  having  its  lower  end 
closed. 

709.  What  pressure  is  ordinarily  used  on  this  type  of 
elevator  ? 

Ans.    150  to  200  Ibs.  per  square  inch. 

710.  How  is  the  top  of  the  cylinder  arranged? 

Ans.  With  a  packing  gland  through  which  the  plunger 
moves  up  and  down. 

711.  What  types  of  elevators  are  in  general  use  for 
passenger  service? 

Ans.     Electric  and  hydraulic. 

712.  How  is  the  capacity  of  a  pump  usually  expressed? 
Ans.     In  gallons  of  water  per  minute  raised  to  a  given 

height. 

713.  What  is  meant  by  the  head  under  which  a  pump 
works  ? 

Ans.  The  vertical  distance  between  the  surface  of  the 
water  in  the  suction  reservoir,  and  that  in  the  discharge 
reservoir. 


106 


Steam  Engineering 


FIG.  514 


Electricity  for  Engineers 

714.  What  is  electricity? 

Ans.  Electricity  is  an  invisible  agent.  Its  exact  na- 
ture is  not  very  well  known,  although  the  laws  govern- 
ing its  action,  the  methods  of  controlling  it,  and  the  ef- 
fects produced  by  it  are  becoming  well  known. 

715.  Is  it  correct  to  use  the  term  quantity  with  refer- 
ence to  electricity? 

Ans.  It  is.  We  may  use  terms  to  designate  definite 
quantities  of  electricity,  passing  through  a  conductor,  in  the 
same  way  that  we  speak  of  gallons  of  water  flowing  through 
a  pipe. 

716.  Is  it  proper  to  assume  that  there  are  large  quanti- 
ties  of  electricity  stored  for  future  use,  in  a  manner  similar 
to  water? 

Ans.  It  is  not,  except  in  a  limited  sense,  as  in  storage 
batteries. 

718.  Define  the  doctrine  of  the  conservation  of  energy. 
Ans.     The  total  quantity  of  energy  in  the  universe  is 

unalterable.     When  energy  is  expended,  or  disappears  in 
one  form,  it  must  reappear  in  another  form. 

719.  In  accordance  with  this  doctrine,  what  would  be 
the  proper  term  to  apply  to  electricity  with  reference  to 
the  physical  requirements  of  man? 

Ans.  It  is  a  useful  agent  for  the  rapid  transmission  of 
stored  up  energy  in  fuel,  water  falls,  etc. 

720.  What  is  the  practical  unit  of  quantity  used  in 
speaking  of  electricity? 

107 


108  Steam  Engineering 

Ans.  The  coulomb.  It  is  that  quantity  of  electricity 
that  would  pass  in  one  second  through  a  circuit  carrying  a 
current  of  one  ampere. 

721.  What  is  an  ampere? 

Ans.  It  is  the  unit  of  volume,  or  rate  of  flow.  A  cur- 
rent of  one  ampere  will  flow  through  a  circuit  whose  re- 
sistance equals  one  ohm,  when  the  electro-motive  force,  or 
pressure  behind  it  equals  one  volt. 

722.  What  is  a  volt? 

Ans.  The  volt  is  the  unit  of  electro-motive  force,  and 
represents  a  pressure  that  will  cause  the  flow  of  one  am- 
pere through  a  circuit  in  which  the  resistance  equals 
one  ohm. 

723.  What  is  an  ohm? 

Ans.  The  ohm  is  the  practical  unit  of  electrical  resist- 
ance. It  is  that  amount  of  resistance  that  would  limit  the 
flow  of  electricity  under  an  electromotive  force  of  one 
volt,  to  a  current  of  one  ampere,  or  to  a  discharge  of 
one  coulomb  per  second.  It  equals  the  resistance  of  a 
column  of  mercury  one  sq.  millimetre  in  area  of  cross  sec- 
tion, and  104.9  centimetres  in  length. 

724.  What  is  the  unit  of  work? 
Ans.    The  foot  pound. 

725.  What  is  the  unit  of  power,  or  rate  of  doing  work? 
Ans.     The  foot  pound,  per  second. 

726.  How  is  the  amount  of  work  that  electricity  is  ca- 
pable of  doing,  measured  ? 

Ans.  By  the  volt-coulomb,  or  Joule.  The  amount  of 
electrical  work  per  second  is  equal  to  the  volt  ampere,  or 
watt. 

727.  What  amount  of  power  developed  is  represented 
by  the  watt? 


What  is  Electricity  109 

Ans.  44.25  foot-lbs.  of  work  per  minute,  or  0.7375  foot- 
Ibs.  per  second. 

728.  What  is  a  magnet  ? 

Ans.  A  mineral  consisting  of  a  combination  of  iron  and 
oxygen. 

729.  What  is  the  chemical  formula  of  a  magnet? 
Ans.     Fe304. 

730.  What  is  a  permanent  magnet? 

Ans.  A  piece  of  steel  that  has  been  charged  with  mag- 
netism, and  retains  it. 

731.  What  is  meant  by  the  poles  of  a  magnet? 

Ans.  All  magnets  tend  to  point  north  and  south,  the 
same  end  always  pointing  in  the  same  direction ;  hence  the 
end  pointing  north  is  called  the  north  pole,  and  the  end 
pointing  south  is  termed  the  south  pole. 

732.  What  peculiar  characteristic  attaches  to  the  poles 
of  magnets  ? 

Ans.  The  north  poles  of  two  magnets  tend  to  repel 
each  other,  and  the  same  is  true  of  the  south  poles.  But 
the  north  pole  of  one  magnet  attracts  the  south  pole  of  an- 
other, like  repels  like,  and  unlike  attracts  unlike. 

733.  What  is  an  electro  magnet? 

Ans.  A  bar  of  iron  surrounded  by  a  coil  of  wire  through 
which  an  electric  current  is  passing. 

734.  What  are  lines  of  force? 

Ans.  They  are  certain  imaginary  lines  passing  through 
the  steel  of  the  magnet  from  its  south  pole  to  its  north  pole, 
and  issuing  from  the  latter  they  curve  around  through 
space  and  return  to  the  south  pole. 

735.  What  is  the  magnetic  circuit  ? 

Ans.  It  is  the  path  of  these  lines  of  force,  around  and 
through  the  magnet.  It  resembles  a  closed  curve,  either  a 
circle,  or  an  ellipse. 


110  Steam  Engineering 

736.  Explain  the  difference  between  the  magnetic  cir- 
cuit and  the  electric  circuit. 

Ans.  The  magnetic  circuit,  or  field  of  force,  that  sur- 
rounds a  magnet  is  maintained  without  the  expenditure  of 
energy,  while  on  the  other  hand  an  electric  current  passing 
upon  its  circuit  develops  energy,  and  energy  must  be  ex- 
pended to  maintain  it. 

737.  Are  there  any  other  points  of  difference  between 
the  two  circuits. 

Ans.  Yes,  the  electric  current  passes  through  a  con- 
ductor in  intensity  proportional  to  the  electro-motive  force 
urging  it,  while  the  magnetic  circuit  passes  through  air, 
or  a  vacuum  in  proportion  to  the  magneto-motive  force 
urging  it. 

738.  What  is  meant  by  the  term  potential  as  applied  in 
electric  practice? 

Ans.    Voltage  or  pressure. 

739.  What  is  the  law  of  induction  ? 

Ans.  When  a  conductor  is  moved  in  a  magnetic  field 
of  force  so  as  to  cut  the  lines  of  force,  there  is  an  electro- 
motive force  impressed  on  the  conductor  in  a  direction  at 
right  angles  to  the  direction  of  motion,  and  at  right  an- 
gles to  the  direction  of  the  lines  of  force. 

740.  What  is  a  dynamo? 

Ans.  A  machine  for  transforming  mechanical  energy 
into  electrical  energy. 

741.  How  is  the  field  of  force  maintained  in  a  dynamo? 
Ans.     By  means  of  electro-magnets. 

742.  Does  not  this  require  the  expenditure  of  energy? 
Ans.    Yes ;  a  certain  amount  of  energy  is  indirectly  ex- 
pended. 

743.  How  are  dynamos  classified? 


The  Dynamo  111 

Ans.    Into  two  grand  divisions,  viz.,  direct  current  dy- 
namos and  alternating  current  dynamos. 

744.  What  is  direct  electrical  current? 
Ans.     A  current  of  unchanging  direction. 

745.  What  is  an  alternating  current  ? 

Ans.     A  current  that  reverses  its  direction  of  flow,  pe- 
riodically, from  20  times  and  upward  per  second. 

746.  Name  the  principal  constituent  parts  of   a  dy- 
namo. 

Ans.     The  armature,  the  field,  the  collecting  rings,  or 
commutator,  and  the  brushes. 

747.  How  is  electro  motive  force  or  current  induced  in 
a  dynamo? 

Ans.     By  rapidly  changing  field  and  armature  relations 
by  means  of  mechanical  energy. 

748.  How  is  the  output  of  a  dynamo  stated? 

Ans.     In  Kilowatts  equal  to  1,000  X  volts  X  amperes. 

749.  How  is  the  output  of  a  motor  statod  ? 

Ans.     In  horse  power,  equal  to  Watts  intake -r- 746  X  ef- 
ficiency expressed  decimally.     (Not  as  a  percentage.) 

750.  What  is  the  voltage  of  a  dynamo?  of  motor? 
Ans.     It  is  the  pressure  that  the  generator  or  alternator 

delivers  at  its  own  terminals.  The  voltage  of  a  motor  is  the 
voltage  which  should  be  applied  to  its  terminals  in  order 
to  develop  full  horse  power. 

751.  What  is  full  load  current  of  dynamo?  of  motor? 
Ans.    Full  load  current  of  a  dynamo  is  that  current 

which  may  be  drawn  steady  for  24  hours  without  causing 
any  part  of  the  machine  to  exceed  a  safe  temperature,  i.  e., 
150°  Fahr.  This  applies  to  factory  motors. 

752.  What  is  meant  by  the  rating  of  a  dynamo  ?    Of  a 
motor  ? 


112  Steam  Engineering 

Ans.  The  product  of  full  load  current  multiplied  by 
the  voltage  expressed  in  Kilowatts  is  rating  of  a  dynamo. 
The  actual  mechanical  horse  power  developed  at  the  pinion 
of  the  motor  as  tested  in  shop. 

753.  What  is  the  armature  core? 

Ans.  The  sheet  iron  body  which  carries  the  armature 
winding,  and  conducts  the  flux  from  pole  piece  to  pole  piece. 

754.  What  is  the  armature  spider  ?  «• 
Ans.     The  casting  consisting  of  hub  and  arms  which 

supports  armature  core. 

755.  What  are  binding  wires? 

Ans.  They  are  narrow  bands  of  phosphor  bronze  wire 
placed  around  the  armature  every  three  or  four  inches  to 
help  bind  the  winding  to  the  core.  They  rest  on  strips  of 
mica,  and  are  sweated  with  solder  all  around. 

756.  What  are  commutator  segments? 

Ans.  The  commutator  segments  or  bars  are  the  copper 
pieces  of  which  the  commutator  is  built. 

757.  What  are  commutator  leads? 

Ans.  They  are  the  ends  of  the  armature  winding  ex- 
tending from  the  core  to  the  lug  of  the  commutator  bar. 

758.  What  are  pole  pieces? 

Ans.  The  end  of  the  magnet  core  nearest  the  armature. 
Usually  larger  than  the  core. 

759.  What  are  magnet  cores? 
Ans.     The  iron  inside  the  field  coil. 

760.  What  is  the  yoke? 

Ans.  The  part  of  magnetic  circuit  connecting  the  mag- 
net cores. 

761.  What  is  the  pitch  of  an  armature  winding? 

Ans.  It  is  the  number  of  teeth  between  the  two  sides  of 
a  formed  coil  plus  one  tooth. 


The  Commutator  113 

Example :  The  two  sides  of  a  coil  are  in  slots  number 
3  and  17,  then  pitch  is  14. 

762.  Is  there  insulation  between  winding  and  core? 
Ans.    Yes.    Mica  or  fuller  board;  there  is  also  the  tape 

on  coil. 

763.  What  insulation  is  there  between  conductors  of 
winding  ? 

Ans.  The  double  cotton  covering  of  each  wire  makes 
four  thicknesses  between  conductors. 

764.  What  is  the  air  gap? 

Ans.  It  is  the  air  space  between  armature  and  pole 
pieces.  In  dynamos  it  is  made  as  small  as  possible  for  ef- 
ficiency. 

In  motors  it  is  not  made  too  small  because  this  tends  to 
make  the  machine  spark  due  to  the  weak  field.  In  D.  C. 
series  motors  it  is  from  %  to  %  of  an  inch,  in  A.  C.  series 
motor  it  is  smaller,  say  1/10  to  %  inch. 

The  larger  the  air  gap  of  a  motor  the  more  the  bearings 
may  wear  before  there  is  danger  of  the  armature  rubbing 
against  the  lower  pole  pieces. 

765.  What  are  field  spools? 

Ans.  The  brass  shells  on  which  the  field  coils  are 
wound. 

766.  What  is  the  commutator? 

Ans.  It  is  a  series  of  copper  bars  placed  parallel  to 
the  shaft,  insulated  from  each  other  and  from  the  frame  of 
the  machine.  Each  is  connected  to  the  winding  and  cur- 
rent flows  from  the  winding  through  them  to  the  brushes. 
It  at  the  same  time  reverses  the  connections  between  the 
brushes  and  the  winding  at  the  proper  times  so  that  the 
brush  always  collects  current. 

767.  What  is  a  collector  or  slip  ring? 


114  Steam  Engineering 

Ans.  A  collector  consists  of  two  or  more  rings  of  copper 
placed  around  the  shaft  and  insulated  from  it,  and  each 
other.  Each  is  connected  to  a  part  of  the  winding.  The 
brushes  rest  on  the  rings. 

They  are  used  to  collect  current  from  a  revolving  arma- 
ture style  of  alternator,  to  feed  current  into  armatures  of 
rotary  converters,  or  the  revolving  fields  of  alternators. 

The  collector  has  no  corrective  influence  and  passes  on 
the  A.  C.  or  D.  C.  current  exactly  as  it  receives  it. 

Single  phase  machines  have  two  rings;  two,  three,  and 
six  phase  machines  have  three  rings. 

768.  Is  there  a  difference  between  no  load  and  full  load 
voltage  of  dynamos? 

Ans.  Yes.  A  shunt  dynamo  gives  highest  voltage  at  no 
load  and  lowest  at  overloads ;  the  series  dynamo  gives  lowest 
at  no  load  and  highest  at  full  load.  The  compound  dy- 
namo is  a  combination  of  series  and  shunt,  and  gives  same 
voltage  at  all  loads. 

An  alternator  acts  like  a  shunt  dynamo. 

769.  What  is  a  field  rheostat? 

Ans.  It  is  a  resistance  in  the  field  circuit  which  can  be 
varied  to  change  the  current,  and  hence  the  field  strength. 
This  alters  the  voltage  of  the  dynamo. 

770.  What  are  commutated  fields? 

Ans.  In  some  motors  the  field  coils  are  arranged  in  sec- 
tions so  that  they  may  be  arranged  in  parallel,  or  series,  or 
in  combinations. 

All  coils  in  parallel  give  the  greatest  current  and  hence 
slowest  speed  of  motor;  all  coils  in  series  give  the  weakest 
field  and  the  fastest  speed. 

771.  What  relation  has  field  strength  to  the  speed  of 
motor  ? 


Armature  Winding  115 

Ans.  The  weaker  the  field  the  faster  the  speed,  for  the 
motor  must  revolve  fast  to  generate  its  proper  counter 
E.  M.  F. 

772.  What  relation  has  armature  strength  to  the  speed 
of  motor  ? 

Ans.  The  greater  the  armature  current  the  higher  the 
speed. 

773.  What  effect  on  the  power  of  motor  does  field,  and 
armature  strength  have? 

Ans.  The  greater  the  field  and  armature  current  the 
greater  the  power. 

774.  What  is  a  ring  winding? 

Ans.  One  which  passes  over  and  under  around  the  core, 
a  space  being  left  between  the  shaft  and  core  to  accommo- 
date the  winding. 

775.  What  is  a  drum  winding? 

Ans.  One  where  all  winding  is  on  the  outer  surface  of 
the  core. 

776.  Upon  what  does  sparkless  commutation  of  current 
depend  ? 

Ans.  (1)  The  more  commutator  bars  the  better,  there 
being  less  voltage  and  therefore  tendency  to  spark  between 
bars.  The  average  railway  motor  has  from  100  to  125 
bars  on  commutator. 

(2)  The  fewer  the  ampere  turns  on  the  armature  in 
comparison  to  the  ampere  turns  on  the  field  the  less  spark- 
ing. 

(3)  The  more  turns  short-circuited  by  the  brush  when 
touching  two  or  more  bars  at  once,  the  greater  the  tendency 
to  spark. 

777.  What  is  a  shunt  field? 

Ans.  One  whose  coils  are  placed  as  a  shunt  across  the 
brushes.  It  carries  a  small  current. 


116  Steam  Engineering 

778.  What  is  a  series  field? 

Ans.  One  which  carries  the  main,  or  nearly  all  the 
main  current,  and  is  placed  in  series  with  the  armature. 
A  small  strip  of  resistance  metal  is  used  sometimes  to  di- 
vert a  portion  of  the  main  current  from  the  series  field. 

779.  What  are  Foucault,  or  eddy  currents? 

Ans.  Local  currents  set  up  within  the  armature,  and 
acting  as  a  hindrance  to  the  generation  of  useful  current. 

780.  How  may  the  electro-motive  force  he  increased  ? 
Ans.     By  increasing  the  speed,  or  by  adding  more  turns 

or  loops  of  wire  to  the  armature  winding. 

781.  What  is  meant  by  self  excitation  of  a  dynamo? 

Ans.  When  the  dynamo  is  standing  still,  the  field  mag- 
nets become  weakly  magnetic,  but  when  the  armature  begins 
to  revolve  a  few  volts  of  electric  current  will  be  sent  through 
the  field  coils,  gradually  increasing  the  magnetic  strength 
until  full  voltage  is  reached. 

782.  What  is  a  series  dynamo  ? 

Ans.  One  in  which  the  same  current  that  travels  the 
main  circuit  also  traverses  the  field. 

783.  Explain  the  action  of  the  shunt  dynamo. 

Ans.  The  field  circuit  is  a  shunt,  and  only  a  portion  of 
the  main  current  passes  through  it. 

784.  How  are  the  fields  of  a  compound  dynamo  ex- 
cited? 

Ans.  The  fields  have  two  distinct  windings ;  one  shunt, 
and  the  other  series. 

785.  What  advantage  pertains  to  the  compound  wound 
dynamo  ? 

Ans.     It  is  practically  self-regulating. 

786.  What  is  the  difference  between  the  dynamo  and 
the  electric  motor?  » 


The  Currents  117 

Ans.  Practically  none  in  the  principles  governing  the 
design  of  the  machines.  Any  dynamo  may  be  used  as  a 
motor,  and  vice  versa. 

787.  State  the  difference  in  their  functions. 

Ans.  The  dynamo  converts  mechanical  energy  into  elec- 
trical energy,  while  the  motor  converts  electrical  energy 
into  mechanical  energy. 

788.  Upon  what  does  the  power  to  be  obtained  from 
a  motor  depend? 

Ans.  Two  things,  viz.,  the  current  flowing  in  its  arma- 
ture coils,  and  the  strength  of  magnetism  developed  in  its 
fields. 

789.  How  is  the  speed  of  motors  controlled? 
Ans.     By  a  starting  box  or  rheostat. 

790.  How  may  the  direction  of  rotation  of  a  motor 
be  reversed?. 

Ans.  By  reversing  the  current  through  either  the  ar- 
mature or  the  fields. 

791.  Upon  what  principle  does  the  alternating  current 
motor  act  ? 

Ans.  Upon  the  principle  of  induction,  having  for  its 
main  accessory  the  rotary  field. 

792.  How  is  a  rotary  field  produced? 
Ans.     By  the  use  of  polyphase  currents. 

793.  Explain  the  meaning  of  the  term  rotary  field. 

Ans.  In  a  rotary  field  the  rotary  action  is  purely  elec- 
trical, the  poles  simply  rotating  around  the  circle.  There 
is  no  rotation  of  the  mechanism  of  the  field. 

794.  What  then  is  a  revolving  field? 

Ans.    A  field  that  revolves  around  an  axis  like  a  wheel. 

795.  What  is  the  leading  characteristic  of  the  direct 
current  ? 


118  Steam  Engineering 

Ans.     It  travels  in  the  same  direction  of  pressure. 

796.  What  is  the  tendency  of  the  current  generated  in 
all  dynamos? 

Ans.    It  is  alternating  in  voltage  or  pressure. 

797.  Explain  the  meaning  of  the  term  alternating  as 
used  in  this  connection. 

Ans.  The  current  starts  at  a  value  of  zero,  rises  to  a 
maximum  of  polarity,  descends  to  a  value  of  zero  again,  and 
changing  in  direction  of  pressure,  rises  to  a  maximum  of 
opposite  polarity,  from  whence  it  drops  to  zero  again. 

798.  How  then  is  direct  current  produced  from  this  al- 
ternating current? 

Ans.  By  means  of  the  commutator  and  brushes  on  the 
direct  current  generator. 

799.  What  is  the  leading  characteristic  of  the  alternat- 
ing current? 

Ans.  Its  voltage  is  continually  changing  at  regular  in- 
tervals from  zero  to  maximum  in  the  direction  of  opposite 
polarity. 

800.  How  is  this  action  best  represented? 

Ans.  By  wave  curves  drawn  above  and  below  a  horizon- 
tal line  representing  zero. 

801.  In  what  manner  does  the  action  of  the  alternating 
current  affect  the  circuit  through  which  it  travels  ? 

Ans.  The  whole  circuit  passes  simultaneously  through 
voltage  values  of  the  cycle  represented  by  the  wave  curve. 

802.  What  is  meant  by  the  frequency  of  an  alternating 
current  ? 

Ans.    The  number  of  waves  or  cycles  per  second. 

803.  What  does  a  frequency  of  60  mean? 


The  Voltage  119 

Ans.  It  means  that  the  voltage  values  pass  through  a 
complete  cycle  in  one  sixtieth  of  a  second,  that  is  60  cycles 
per  second. 

804.  What  is  meant  by  alternations? 

Ans.  The  number  of  reversals  per  minute  in  the  di- 
rection of  pressure. 

805.  How  many  alternations  would  there  be  in  a  cur- 
rent having  a  frequency  of  60  ? 

Ans.     7,200. 

806.  What  is  meant  by  a  "period?" 

Ans.  The  time  in  seconds  or  fractions  of  a  second  re- 
quired to  pass  through  a  complete  cycle. 

807.  What  is  meant  by  current  wave? 

Ans.  It  means  the  actual  values  of  the  current  as  shown 
by  the  volt-meter  and  ammeter. 

808.  Do  these  equal  the  values  of  the  theoretical  wave 
curve  ? 

Ans.     They  do  not,  reaching  about  70  per  cent. 

809.  Why  is  this? 

Ans.  It  is  due  to  the  influence  of  the  iron  magnetic 
circuit  caused  by  the  connections  of  induction  motors,  arc 
lamps,  and  other  electrical  apparatus. 

810.  What  is  meant  by  effective  current? 

Ans.  The  voltage  and  volume  as  shown  by  the  volt- 
meter and  ammeter. 

811.  In  what  respect  is  the  maximum  voltage  as  shown 
by  the  calculated  wave  curve  useful? 

Ans.     It  is  useful  in  testing  insulating  materials. 

812.  What  is  meant  by  phase  in  electric  practice? 
Ans.     It  denotes  the  relative  position  of  a  current  wave. 

with  respect  to  the  wave  of  electro-motive  force  producing 
it. 


120  Steam  Engineering 

813.  When  is  a  current  in  phase? 

Ans.  When  the  two  waves  just  mentioned  start  at  zero 
and  reach  their  maximum  values  at  the  same  instant. 

814.  What  is  meant  by  lag? 

Ans.  When  the  current  wave  lags  behind  the  voltage 
wave. 

815.  What  is  meant  by  lead? 

Ans.  When  the  current  wave  is  ahead  of,  or  leads  the 
voltage  wave. 

816.  What  is  the  meaning  of  two  and  three  phase  cur- 
rents ? 

Ans.  When  the  winding  of  the  armature  is  such  that 
two  or  three  electro-motive  forces  in  quadrature  with  each 
other  are  simultaneously  produced  by  the  generator  the  cur- 
rents thus  produced  may  be  distributed  over  four  or  six 
conductors,  a  pair  for  each  current. 

817.  Is  it  necessary  to  have  a  pair  of  conductors  for 
each  current  in  two  and  three  phase  current  work  ? 

Ans.  No.  By  means  of  the  Y  winding  it  is  possible  to 
distribute  the  current  over  three  wires,  each  wire  acting  as 
a  main,  and  return  wire  for  one  of  the  others. 


Armature  Design  and  Construction 

818.  Can  the  properties  of  a  dynamo  be  accurately  cal- 
culated from  any  of  the  formulas  given  for  that  purpose? 

Ans.  No.  The  accurate  design  of  a  new  type  of  dynamo, 
and  an  armature  as  well,  is  as  much  a  matter  of  experiment 
as  it  is  of  calculation. 

819.  Why  is  this? 

Ans.  There  are  so  many  factors  involved  in  the  calcu- 
lation that  cannot  be  accurately  determined  until  a  ma- 
chine of  the  exact  dimensions  of  the  one  under  considera- 
tion has  been  built. 

820.  What  are  the  principal  factors  that  are  so  trouble- 
some to  determine? 

Ans.  The  permeability  of  the  iron,  the  resistance  of 
the  magnetic  circuit,  the  tendency  to  leakage  of  the  lines 
of  force,  the  exact  proportion  of  the  dead  wire,  the  reaction 
of  the  armature,  the  losses  due  to  Foucault  currents. 

821.  Are  not  the  causes  of  all  these  losses  well  under- 
stood ? 

Ans.  They  are,  and  it  is  easy  enough  to  tell  what  must 
be  done  to  lessen  any  or  all  of  them.  It  is  merely  their 
exact  value  which  is  indeterminate  until  the  machine  in 
question  is  in  operation. 

822.  What  is  the  chief  precaution  which  must  be  taken 
on  this  account. 

Ans.  It  is  necessary  to  leave  some  part  of  the  controlling 
influences  so  that  they  can  be  readily  varied  and  thus  adjust 
the  machine  so  that  it  will  be  exactly  right  when  it  is  finally 
finished. 

823.  How  can  this  best  be  done? 

Ans.     Since  it  is  manifestly  very  troublesome  to  rewind 

121  ' 


122  Steam  Engineering 

an  armature,  if  perchance  too  great  or  too  small  a  number 
of  wires  have  been  placed  upon  it,  the  proper  factors  to  be 
arranged  to  be  variable  are :  the  speed,  and  the  strength  of 
the  field.  In  some  cases  the  speed,  even,  is  not  changeable, 
and  the  whole  duty  of  compensating  for  misjudgment  in 
the  calculations  falls  upon  variations  of  the  field  strength. 

824.  Can  the  whole  regulation  be  accomplished  in  this 
way? 

Ans.  It  can,  and  in  most  cases  this  is  the  method  relied 
upon.  It  is  very  easily  accomplished  by  this  method  if  we 
arrange  to  have  the  fields  magnetized  to  only  a  low  degree 
of  saturation.  By  doing  this,  however,  we  are  led  to  provide 
field  magnets  whose  capacity  is  far  in  excess  of  what  we 
believe  to  be  necessary  and,  therefore,  more  expensive.  So 
that  again  in  the  last  consideration  it  behooves  us  to  experi- 
ment before  we  definitely  determine  the  exact  proportion 
of  our  dynamo  or  motor. 

825.  Are  there  any  formulae  that  can  be  used  in  deter- 
mining the  exact  proportions? 

Ans.  There  are,  and  they  are  given  below.  These  will 
materially  assist  the  student  in  forming  an  idea  how  the 
different  parts  can  be  adjusted  to  bring  about  the  desired 
final  result.  For  the  following  formulas  we  shall  adopt  the 
attached  set  of  symbols: 

Let  F=the  total  number  of  lines  of  force,  or  flux, 
V=the  number  of  volts  to  be  generated, 
S=the  number  of  slots  in  the  armature, 
R.P.S.=:the  number  of  revolutions  per  second, 
W=the  number  of  wires  per  slot. 

Then,  to  find  the  number  of  wires  necessary  per  slot  where 
the  speed  and  flux  are  fixed: 

108XV 

"TP" 

~ 


Formulae  123 

To  find  the  necessary  speed  where  the  number  of  wires,  and 
the  flux,  are  fixed: 

108XV 

R.  p.  S.r= — 

FXSXW 

To  find  the  necessary  strength  of  field,  where  the  wires 
and  speed  are  fixed : 

F==     1Q8xy 
SXR.P.  s.xw 

To  find  the  volts  generated : 

FXSXWXR.P.  s. 


V=- 


108 

826.  Are  these  formulae  used  in  actual  practice  to  deter- 
mine the  size  of  wire,  speed,  etc.  ? 

A ns.  These  formulas  are  of  value  principally  in  check- 
ing up  the  actual  calculations  made. 

827.  How.  is  an  armature  actually  designed? 

A  ns.  In  actual  practice  whenever  a  new  dynamo  or 
motor  is  to  be  constructed  it  is,  so  to  speak,  built  up  around 
the  armature.  That  is  to  say,  the  armature  must  first  be 
designed,  and  the  other  parts  made  to  fit  around  it. 

828.  What  is  the  principal  consideration  to  be  taken 
into  account? 

Ans.  In  order  to  deliver  a  certain  current,  the  number 
of  poles,  etc.,  being  fixed,  which  is  with  rare  exceptions  the 
case,  we  must  use  a  certain  size  wire. 

829.  Is  there  no  choice  whatever  in  the  size  of  wire 
for  a  given  current? 

Ans.  There  is  some  choice.  In  most  cases  the  heating 
of  the  wire  on  the  armature  determines  the  size  of  wire  to 
be  used;  in  other  cases  it  is  the  drop  in  potential  at  the 
terminals  of  the  armature  that  governs. 


124  Steam  Engineering 

830.  How  does  the  size  of  wire  affect  the  heating,  and 
the  loss  of  potential? 

^4.715.  Both  of  these  losses,  and  the  troubles  occurring 
from  them,  are  lessened  by  selecting  wires  of  greater 
diameter. 

831.  How  do  you  proceed  to  calculate  the  necessary  size 
of  wire? 

Ans.  The  number  of  wires,  and  the  dimensions  of  the 
armature  for  any  given  purpose  can  be  found  by  trial  cal- 
culations only.  By  this  we  mean  that,  unless  we  are  very 
lucky,  we  shall  have  to  make  a  number  of  calculations, 
using,  perhaps,  different  dimensions  and  wires  before  we 
get  the  result  that  suits  us  best. 

S32.     Give  an  example. 

Ans.  As  an  example  let  us  take  an  armature  8  inches 
in  diameter  and  8  inches  in  length  and  see  what  it  will 
do  for  us.  Such  an  armature  has  a  cross-section  of  64  sq. 
inches  and,  assuming  a  flux  of  30,000  lines  of  force  per 
square  inch,  we  have  a  total  flux  of  1,920,000  lines  through 
the  armature.  We  first  find  how  often  one  wire  must  cut 
this  number  of  lines  of  force  to  generate,  say,  110  volts. 
To  do  this  we  first  divide  110X100,000,000  (which  is  the 
total  number  of  lines  to  be  cut  per  second)  by  the  total 
flux,  1,920,000,  and  obtain  as  the  result  5728.  Next,  to 
get  the  necessary  number  of  wires  to  be  placed  upon  the 
armature,  we  must  divide  this  quotient  (5728)  by  the 
number  of  revolutions  the  armature  makes  per  second.  If 
our  armature  revolves  at  the  rate  of  twenty  revolutions  per 
second  (1,200  per  minute)  we  shall  need  one-twentieth 
of  5,728  wires  placed  upon  it.  This  amounts  to  286.  As 
our  armature,  8  inches  in  diameter,  has  a  circumference  of 
25.12  inches,  this  gives  us  a  wire  running  about  11  per 


Wire  Used  125 

inch.  If  there  is  to  be  but  one  layer,  this  gives  a  number 
12  wire.  As  the  two  sides  of  the  armature  are  in  parallel 
we  have  a  capacity  of  2  times  14.31  amperes  according  to 
Table  50.  If  we  decide  to  use  two  layers,  we  can  take  a 
No.  6  wire,  5.5  per  inch,  and  obtain  a  capacity  of  56.55 
amperes.  It  may  be  stated  in  explanation  of  the  calcula- 
tions here  made  that  each  wire  in  the  course  of  one  revolu- 
tion of  the  armature  cuts  the  total  flux  two  times;  but  as 
the  two  halves  of  the  armature  are  in  parallel,  each  side 
must  produce  the  full  voltage  by  itself. 

833.  How  much  radiating  surface  is  usually  allowed  per 
watt  of  energy  used  up  ? 

Ans.  That  depends  very  much  on  the  work  for  which 
the  armature  is  intended.  If  it  is  for  a  railway  motor, 
which  is  entirely  enclosed,  and  almost  constantly  in  use,  it 
is  much  more  than,  for  instance,  an  elevator  in  a  private 
residence  where  there  is  but  very  little  use,  and  only  at  long 
intervals,  so  that  the  armature  has  time  to  cool  off  between 
one  run  and  another.  Table  50  is  based  upon  the  require- 
ment that  there  shall  be  three  square  inches  of  radiating 
surface  for  each  watt  of  energy  expended  in  the  coils. 

834.  What  radiating  surface  is  allowed  for  each  watt 
expended  in  the  case  of  an  armature? 

Ans.  This  amount  varies  in  different  machines,  being 
as  low  as  1  square  inch  per  watt,  and  as  high  as  three  square 
inches  per  watt.  About  1.75  square  inches  per  watt  ex- 
pended can  be  considered  as  a  fair  average  for  armatures 
and  about  3  inches  per  watt  expended  for  field  coils. 

835.  How  is  the  table  referred  to  (Table  50)  made  up? 
Ans.    This  table  is  figured  from  the  formula, 


126  Steam  Engineering 

R  S  being  the  radiating  surface,  and  R  the  resistance  of  a 
unit  of  length  of  the  wire  under  consideration.  This  form- 
ula gives  the  current  allowed  where  the  wire  is  wound  in 
one  layer.  As  we  add  more  layers  we  must,  with  each  suc- 
cessive layer,  reduce  the  current,  so  that  the  square  of  the 
current  multiplied  by  the  resistance  (which  equals  the 
watts)  shall  remain  always  the  same,  because  increasing 
the  depth  of  the  winding  does  not  affect  the  radiating  sur- 
face of  the  coil. 

836.  The  table  gives  the  carrying  capacity  only  to  a 
depth  of  six  layers ;  how  is  the  carryng  capacity  of  a  greater 
number  of  layers  to  be  found? 

Ans.  To  do  this  we  refer  to  Table  50  and  select  from  the 
column  headed  P  the  number  pertaining  to  the  wire  in 
question.  This  number  represents  the  square  of  the  cur- 
rent permissible  with  one  layer  of  wire.  Divide  this  num- 
ber by  the  number  of  layers  it  is  intended  to  use,  and  extract 
the  square  root  of  the  number  so  found.  The  result  will  be 
the  carrying  capacity  of  the  wire  in  question,  wound  to  a 
depth  of  that  number  of  layers.  As  a  general  guide  we  may 
bear  in  mind  that,  as  we  multiply  the  number  of  layers  by 
4,  16,  64,  256,  we,  each  time,  decrease  by  one-half  the 
carrying  capacity  of  the  wire.  From  this  we  can  see  that 
the  capacity  of  the  wires  after  a  certain  number  of  layers 
have  been  considered,  decreases  very  slowly,  though  very 
fast  with  the  first  few  layers. 

837.  Is  there  need  of  very  great  accuracy  in  these 
calculations  ? 

Ans.  Great  accuracy  is  not  necessary  in  these  calcula- 
tions. We  can  always  lengthen  our  armature  a  little  by 
adding  a  few  punchings,  should  the  potential  be  insufficient, 
and  we  can  always  vary  the  speed  and  strength  of  field  con- 


Tables 


B.  &  S.  Gauge. 


Diameter  bare. 


Resistance   per 
foot  140°   F. 


Diameter  D.  C.  C 


'tOtOD9COj&.CNpS;^pOpU>i 


MM  MM  tO  tO  CO 
M  M  M  M  U>  IO  »O  CO  ^  *•  CT  ^  00  JO  M  OS  OS  CD  W  ^  tC> 


1—  ^  i—  ^  H^  H*  tC  t  C  fC 
»-*  M  M  M  to  tO  03  03  rf»-  O<  O5  -1  00  O  Jd  4»-  O>  O  CO  00 


Number  of  wires 
per  inch. 


128 


Steam  Engineering 


jaSS1 


10^5^04  THrH 


stun)    jo 


oo^<NO 


CO  «5  O  O  rH  00  »O  CO  rH  O5  t-i  CD  irf  -^ 


D  * 


t-i;PlOLO'*-*CO 
OOOOOOO 


-s  ^  - 


Armature  Winding 

eiderably.  Adding  to  any  of  these  would  tend  to  increase 
the  E.  M.  F.  of  the  armature,  but  not  its  capacity  in 
amperes. 

838.  If  the  capacity  of  the  armature  is  not  sufficient, 
how  do  we  proceed  ? 

Ans.  Take  the  next  larger  wire,  or  such  a  wire  as  will 
give  the  desired  capacity,  and  from  the  diameter  of  this 
wire  figure  out  a  new  armature.  By  using  the  same  num- 
ber of  wires  of  a  larger  diameter,  a  greater  cross-section  of 
armature  is  obtained. 

839.  Do    these    considerations    apply    equally    well, 
whether  an  armature  is  slotted,  or  not  ? 

Ans.  The  only  difference  is  that  with  a  slotted  arma- 
ture it  is  necessary  to  take  into  consideration  the  length  of 
the  winding  space  in  the  slots  only,  not  the  total  circum- 
ference of  the  armature.  There  is  also  considerable  loss  of 
flux  through  the  teeth  of  the  armature  so  that  the  flux  must 
be  assumed  less.  A  great  flux  is  obtainable,  however,  with 
the  same  field  winding,  as  the  magnetic  circuit  of  a  dynamo 
with  a  slotted  armature  has  less  resistance. 

840.  How  do  you  proceed  in  the  case  of  a  slotted  arma- 
ture? 

Ans.  If  we  have  an  armature  provided  with  slots  of  a 
fixed  size  we  can  but  arrange  to  accommodate  ourselves  to 
it  as  best  we  may.  It  may  be  that  the  slots  are  of  such  size 
that  the  wire  we  have  selected  through  our  calculation  will 
not  fill  out  the  slot  well,  and  we  must,  therefore,  try  some 
other  size  wire.  In  this  case  it  will  be  preferable  to  select 
a  larger  size  wire  if  practicable.  This  had  best  be  tried  by 
actual  experiment.  As  the  wire  often  will  not  fill  out  the 
slot  quite  fully,  calculations  are  not  exactly  reliable.  Any 
deficiency  can,  of  course,  be  made  up  by  filling  in  with  insu- 


130  Steam  Engineering 

lation.    The  number  of  wires  per  slot  is  found  by  dividing 
the  total  number  of  wires  by  the  number  of  slots. 

841.  How  can  the  size  of  a  slot  capable  of  holding  a 
certain  number  of  wires  be  determined? 

Ans.  The  approximate  depth  of  the  slot  can  be  obtained 
by  multiplying  the  diameter  of  the  wire  to  be  used  by  .86 
and  this  by  the  number  of  layers  placed  over  each  other. 
The  result  will  be  exact  if  the  wires  lie  as  shown  in  Figure 
512.  The  width  of  the  slot  can  be  found  by  multiplying  the 
diameter  of  the  wire  by  the  number  of  turns  per  layer.  It 
will  be  seen  from  the  figure  that  each  alternate  layer  will 
contain  one  turn  less  than  the  first. 

842.  Can  slots  be  proportioned  so  that  they  will  accom- 
modate any  number  of  wires? 

Ans.  The  slots  must  be  proportioned  to  the  number 
of  wires  to  be  used,  and  the  number  of  wires  per  slot  must 
be  carefully  considered.  If  the  number  of  turns  per  slot 
are  few,  the  wires  should  be  placed  as  shown  in  Figure  513. 
If  there  are  many,  according  to  Figure  512.  Which  of  these 
two  methods  is  to  be  used  will  have  a  bearing  on  the  num- 
ber of  wires  per  slot.  The  total  number  must  be  a  multiple 
of  the  number  of  layers. 

843.  After  we  have  selected  our  wire,  and  determined 
the  number  of  wires  to  be  used,  can  we  form  some  idea  of 
what  the  losses  in  the  armature  will  be? 

Ans.  We  can  easily  figure  the  approximate  loss  of  volt- 
age in  the  armature  from  the  size  of  wire  to  be  used.  To 
do  this  we  first  find  from  Table  50  the  resistance  per  foot  of 
the  wire  in  question,  and  then  measure  the  length  of  wire 
in  one  coil  and  multiply  the  resistance  by  the  number  of 
feet.  If  we  have  a  bi-polar  armature  we  again  multiply 
this  by  half  the  number  of  coils  (the  two  sides  being  in 
parallel).  Since  the  loss  in  voltage  is  equal  to  the  amperes 


Armature  Winding  131 

multiplied  by  the  resistance,  we  need  but  to  multiply  the 
resistance  so  found  by  half  the  total  current  to  find  the 
loss  in  voltage  that  will  occur.  This  loss  is,  of  course,  in 
direct  proportion  to  the  current.  This  loss  is  not  of  much 
importance  in  ring  armatures,  or  in  drum  armatures  either, 
when  they  are  working  with  small  currents,  or  on  constant 
current  work  such  as  arc  lighting;  but  with  heavy,  and 
variable  currents  it  is  a  very  important  matter,  and  the 
lower  the  losses  can  be  kept,  the  better. 

844.  Are  there  any  special  considerations  to  be  borne 
in  mind  while  winding  the  different  coils? 

Ans.  It  is  quite  important  to  see  that  each  coil  contains 
the  same  number  of  turns,  and  that  these  fill  out  the  same 
relative  space. 

845.  Why  is  this  so  important? 

Ans.  We  have  already  seen  that  the  two  halves  of  the 
armature  are  generating  in  parallel,  that  is,  the  currents 
from  the  two  sides  meet  at  the  positive  brush  and  flow  out 
to  the  line,  and  return  by  the  negative  side  to  the  armature. 
If  now  there  are  fewer  turns  of  wire  on 'one  side  than  on 
the  other,  or  if  there  is  one  weak  coil  in  the  armature,  one 
side  or  the  other  will  always  be  generating  a  greater  E.  M.  F. 
than  the  other  and  consequently  current  from  the  high  pres- 
sure side  will  flow  through  the  winding  of  the  low  side. 
To  see  this  more  clearly  refer  to  Figure  514.  On  the  arma- 
ture there  shown,  there  are  16  coils.  If  this  armature  is  to 
generate  40  volts,  each  coil  will  be  called  upon  to  produce  5 
volts.  Now  suppose  one  of  the  coils  to  be  cut  out  of  the 
circuit  entirely.  It  is  clear  that  at  all  times  except  when 
the  dead  coil  is  at  the  neutral  points,  there  are  8  coils  gen- 
erating on  one  side  against  7  on  the  other;  i.  e.,  40  volts 
against  35.  In  order  to  find  the  current  that  would  flow  in 
such  an  armature  while  on  open  circuit,  subtract  the  low 


132  Steam  Engineering 

voltage  from  the  high,  which  leaves  an  active  voltage  of  5. 
If  the  resistance  of  the  armature  were  .1  ohm  a  current  of 
50  amperes  will  be  circulating  a  great  part  of  the  time. 

846.  Why  would  this  not  be  a  constant  current  ? 

Ans.  For  the  reason  that  this  current  would  be  con- 
stantly changing  in  direction,  because  the  strong  side  of  the 
armature  would  be  first  on  one  side,  and  then  on  the  other, 
of  the  fields.  On  open  circuit  a  perfect  armature  would 
generate  no  current  whatever;  with  an  armature  as  de- 
scribed the  current  mentioned  would  always  be  flowing 
toward  the  coil  which  is  cut  dead. 

The  current  would  be  changing  in  strength,  because  dur- 
ing the  time  the  dead  coil  is  short  circuited  by  a  brush  it 
would  be  balanced  by  another  coil  under  the  opposite  brush 
which  for  the  moment  is  also  dead.  Consequently  during 
that  time  the  armature  would  not  be  generating  at  all. 

847.  How  would  this  inequality  of  generation  manifest 
itself  if  the  dynamo  were  generating  current  ? 

Ans.  If  the  dynamo  were  generating  current  this  con- 
dition would  greatly  reduce  its  capacity.  The  current  flows 
only  in  obedience  to  the  pressure,  and  as  this  would  be 
variable  the  current  would  of  course  also  be  variable. 

848.  Are  differences  in  potential  between  different  parts 
of  an  armature  caused  by  any  other  conditions  in  the  ar- 
mature ? 

Ans.  Such  differences  are  sometimes  caused  by  the  loca- 
tion of  the  wires  of  different  coils.  Other  things  being  equal 
the  E.  M.  F.  generated  by  any  coil  varies  with  its  distance 
from  the  center  of  the  armature.  It  can  readily  be  seen 
that  the  farther  a  wire  is  from  the  center,  the  greater  will 
be  the  area  enclosed  and  therefore  the  greater  the  number 
of  lines  of  force  cut  by  it. 


Armature  Winding  133 

849.  What  other  cause  is  there  for  inequality  of  genera- 
tion? 

Ans.    Another  cause  for  inequality  of  generation  be- 
tween different  coils  lies  in  a  difference  of  resistance. 

850.  Does  this  affect  the  generation  on  open  circuit? 
Ans.    It  Joes  not.    We  have  already  seen  that  the  loss 

in  potential  in  any  circuit  is  proportional  to  the  current 
flowing,  multiplied  by  resistance  of  the  circuit  in  which  it 
flows.     Therefore  the  drop  in  potential  in  any  coil  is  in 
proportion  to  the  current  being  taken  from  it.    If  one  coil 
therefore  ias  a  much  higher  resistance  than  the  others  its 
potential  tfill  fall  much  more,  and  the  side  of  the  armature 
on  whict  it  happens  to  be  will  be  of  lower  E.  M.  F.  than 
the  othe1,  and  there  will  be  the  same  tendency  to  a  vacillat- 
ing current  as  in  the  case  of  coils  of  uneven  number  of 
turns.  The  variations  will,  however,  not  be  near  so  great, 
for  ar  excessive  current  flow  from  the  strong  side  will  re- 
duce "he  pressure  on  that  side,  and  the  checking  of  the  cur- 
*ent  on  the  low  side  will  raise  the  pressure  there,  so  that  a 
oalance  will  be  obtained  without  any  great  current  flow. 
The  main  danger  of  introducing  inequality  in  the  resistance 
of  the  winding  lies  in  the  winding  of  the  inside  of  the  coil 
with  Gramme  ring  armatures.    The  space  for  the  winding 
at  this  point  is  necessarily  of  a  different  shape  than  that 
on  the  outside,  and  there  are  also  the  spokes  of  the  arma- 
ture to  contend  with. 

851.  How  many  methods  of  armature  winding  are  in 
general  use  ? 

.4ns.  The  methods  of  armature  winding  are  very  numer- 
is.  For  the  present  we  shall  confine  ourselves  to  the 
ethods  used  with  hand  winding  on  cylinder  armatures. 

852.  Which  is  the  most  simple  of  these  windings? 


134 


Steam  Engineering 


Am.  The  simplest  one  of  these  windings  is  that  shown 
in  Figure  534,  and  we  shall  take  this  one  for  the  purpose 
of  demonstration.  It  will  be  noticed  that  in  this  figure  there 
are  12  slots  in  the  armature  and  6  commutator  sections, 
indicated  by  the  wires  twisted  together. 

853.  Is  it  necessary  that  this  proportion  of  slots  and 
armature  coils  exist? 


FIG.  534 


Ans.  It  is  not;  in  fact  it  is  not  at  all  desirable  that  this 
proportion  should  exist,  but  this  proportion  is  very  con- 
venient for  winding,  as  we  shall  see. 

Begin  winding  by  selecting  two  of  the  slots  located 
opposite  each  other,  as  shown  in  the  figure,  and  starting 
at  1  wind  into  those  slots  as  many  turns  of  wire  as  has  been 
determined  there  should  be  and  bring  the  last  end  of  the 


Armature  Winding  135 

coil  to  the  commutator  section  next  the  one  from  which  we 
etarted. 

854.  Should  this  be  to  the  one  in  front  of,  or  behind 
the  section  from  which  the  winding  started  ? 

Ans.  This  is  immaterial.  In  actual  practice  there 
should  not  be  any  commutator  sections  in  place  while  wind- 
ing. They  would  be  very  much  in  the  way.  Instead,  tie  the 
two  ends  of  the  coil  together  and  properly  mark  the  be- 
ginning and  end. 

855.  Are  all  coils  wound  in  the  same  way? 

Ans.  They  are;  but  in  this  case  we  must  skip  one  slot 
at  each  subsequent  coil,  in  order  to  make  them  come  out 
right  in  the  end.  That  is  to  say,  if  the  first  coil  is  wound 
into  1,  1,  the  second  must  be  wound  into  2,  2,  the  third 
into  3,  3,  etc. 

856.  Why  is  this? 

Ans.  As  each  coil  fills  out  two  slots,  we  have  with  the 
third  coil  finished  half  of  the  armature.  If  we  were  to  wind 
the  slots  in  consecutive  order,  the  connections  for  the  com- 
mutator would  all  come  on  one  side,  and  we  could  do  noth- 
ing with  the  armature.  As  we  now  continue  in  the  order 
we  have  started  we  finally  complete  the  entire  winding  and 
have  the  beginning  and  end  of  one  coil  opposite  each  com- 
mutator section.  We  can  now  fasten  the  beginning  of  the 
first  coil  to  its  proper  commutator  section,  and  the  end  of 
it  to  the  next  one.  It  will  be  immaterial  whether  this  be  to 
the  section  ahead,  or  behind  the  starting  section,  but,  which- 
ever way  we  start,  we  must  be  sure  to  continue  in  the 
same  way. 

857.  This  being  the  most  simple  method  of  armature 
winding,  why  are  not  all  armatures  wound  in  this  way? 

Ans.    The  great  objection  to  an  armature  wound  in  this 
way  is  that  the  coils  become  too  large. 


136  Steam  Engineering 

858.  Why  are  large  coils  objectionable? 

Ans.  In  order  to  understand  why  large  coils  are  objec- 
tionable we  refer  to  the  commutator  shown  at  the  right  of 
Figure  534.  Here  a  brush  is  shown  bridging  two  commu- 
tator sections  and  short  circuiting  the  coil  connected  to 
them.  The  coil  indicated  by  the  black  line  is  the  same  one 
shown  in  the  slots  1,  1,  and  the  connections  are  identical. 
It  can  readily  be  seen  that  all  of  the  coils  will  in  turn 
become  short  circuited  in  the  same  way  in  the  course  of 
every  revolution  of  the  armature. 

Now  in  the  first  place  assume  that  the  coil  when  thus 
short  circuited  is  in  an  entirely  dead  part  of  the  field. 
When  a  brush  short  circuits  such  a  coil  it  takes  all  the 
current  away  from  it.  When  the  brush  leaves  the  forward 
section  of  the  commutator  this  short  circuit  must  be  broken, 
and  current  must  be  again  established  through  the  coil. 
As  every  coil  possesses  some  inductance  (which  acts  for  an 
instant  like  a  very  high  resistance),  there  is  a  tendency  for 
the  current  in  that  half  of  the  armature  to  jump  across  the 
insulation  between  the  commutator  sections,  rather  than 
pass  through  the  coil.  If  this  occurs  there  is  destructive 
sparking.  The  greater  the  number  of  turns  of  wire  in  any 
coil,  the  greater  will  be  the  likelihood  of  this  taking  place. 

859.  Is  this  the  main  reason  why  the  coils  on  an  arma- 
ture should  be  made  up  of  few  turns  of  wire  ? 

Ans.  It  is  not.  The  most  important  reason  for  this  is 
the  following :  If  the  coil  is  not  in  an  entirely  "dead"  part 
of  the  field  there  is  always  some  current  generated  in  it 
during  the  time  the  brush  is  in  the  position  discussed  above. 
This  current  circulates  in  the  coil  during  the  time  the 
brush  holds  it  on  short  circuit,  without  appearing  in  the 
outer  circuit,  and  is  therefore  a  dead  loss.  It  furthermore 


Armature  Winding 


137 


tends  to  heat  the  coils.  Because  two  of  the  coils  are  nearly 
always  on  short  circuit  in  this  way,  the  loss  and  the  heating 
are  considerable  when  the  coils  are  large.  When  these  cur- 
rents are  broken  by  the  commutator  section  sliding  from 
under  the  brush,  they  also  make  themselves  evident  by 
severe  sparking,  if  the  coils  are  large. 


FIG.  535 

860.  Are  there  any  more  reasons  why  large  coils  are 
objectionable  ? 

Ans.  Another  reason  why  large  coils  in  an  armature 
are  objectionable  can  best  be  understood  by  reference  to 
Fig.  535.  A  simple  dynamo  such  as  is  depicted  in  this 
figure  delivers  a  current  graphically  illustrated  by  Fig.  536. 
It  will  be  seen  that  this  is  really  an  intermittent  current. 
This  is  because  the  dynamo  has  but  one  coil,  and  while 


138  Steam  Engineering 

this  is  at  the  neutral  points,  nothing  is  being  generated. 
The  current  therefore  fluctuates  from  0  to  its  maximum. 
If  we  add  one  more  coil  the  current  line  becomes  as  shown 
in  Fig.  537,  and  the  greater  the  number  of  coils  the  smaller 
becomes  the  percentage  of  non-generating  coils,  and  the 
nearer  does  the  current  line  approach  a  straight  line  show- 
ing a  steady  value. 

861.  Why  cannot  small  coils  be  wound  in  the  manner 
shown  in  Fig.  534. 

Ans.  It  is  desirable  to  make  the  coils  as  small  as  pos- 
sible. The  ideal  coil  would  consist  of  only  one  turn.  Now 

A/WWV\A 

FIG.  536 


FIG.  537 

as  long  as  we  wind  only  one  coil  into  one  slot  we  shall 
have  the  coils  needlessly  large.  The  number  of  coils  is 
limited  by  the  number  of  commutator  sections,  and  unless 
we  wind  two  coils  into  each  slot  (as  we  can  see  from  Fig. 
534)  we  can  have  but  half  as  many  commutator  sections 
as  there  are  slots.  In  order  to  get  a  small  coil  it  is  there- 
fore necessary  to  get  two  coils  into  each  slot. 

862.     Can  this  be  done  in  more  than  one  way? 

Ans.  This  can  be  done  according  to  any  of  the  plans 
shown  in  Fig.  538.  In  this  figure  the  black  and  white 
circles  respectively  represent  the  wires  of  the  two  different 
°oils  wound  into  the  same  slot. 


Armature  Winding  139 

We  have  already  seen  under  ring  armatures,  that  wires 
of  different  coils  should  all  be  of  the  same  distance  from 
the  center  of  the  armature,  so  as  to  cut  the  same  number 
of  lines;  it  follows,  therefore,  that  the  plan  showing  one 
coil  wound  over  the  other  should  not  be  used  where  it  can 
be  avoided. 

863.    How  do  you  manage  to  place  two  coils  in  one  slot? 

Ans.  In  order  to  understand  exactly  how  this  is  done 
let  us  consult  Fig.  539.  This  figure  is  a  duplicate  of  Fig. 
534  with  the  exception  that  now  we  have  as  many  com- 
mutator sections  as  there  are  slots  in  the  armature.  The 


black  circles  represent  the  wires  of  one  set  of  coils,  and  the 
light  those  of  the  other. 

The  simplest  method  of  winding  two  coils  into  one  slot 
is,  first  to  wind  one  coil  complete,  filling  half  the  slot,  then 
turn  the  armature  half  way  round  and  wind  the  second 
coil  over  the  first.  As  this,  however,  gives  two  coils  of  dif- 
ferent lengths  and  resistance,  and  also  cutting  a  different 
number  of  lines  of  force,  such  a  winding  is  seldom  used. 
A  better  way  is  the  following:  Cut  two  wires  of  sufficient 
length  so  that  each  will  make  one  coil,  place  the  armature 
upon  two  crossbars  of  convenient  height  so  that  it  can  be 


140 


Steam  Engineering 


easily  turned  over  when  required.  Mark  all  of  the  slots 
with  appropriate  numbers  according  to  the  plan  of  wiring 
selected,  so  there  may  be  no  confusion  when  the  work  is 
started.  A  very  good  plan  is  shown  in  Fig.  534.  This 
plan  gives  the  smallest  head  of  any  because  there  are  al- 
ways two  coils  running  parallel  to  each  other  across  the 
ends  of  the  armature.  Thus  we  have  three  layers  of  coils 

1 


FIG.  539 


crossing  over  each  other,  while  with  any  of  the  others 
we  should  have  six.  But  in  order  to  get  the  advantage  of 
this  smaller  head,  we  cannot  wind  the  coils  in  the  order 
given  in  the  explanation  of  this  winding.  It  becomes  neces- 
sary to  wind  completely,  at  the  same  time,  the  two  coils 
that  are  running  parallel  with  each  other  across  the  ends. 
To  do  this  requires  more  experience  and  forethought,  than 
the  way  previously  described. 


Armature  Winding  141 

Begin  the  winding  with  the  coil  marked  1,  and  make 
one  complete  turn  and  fasten  the  two  ends  of  the  wire  to- 
gether temporarily  if  more  turns  are  to  follow,  or  fas- 
ten each  to  its  proper  place  on  the  commutator,  if  there 
is  to  be  but  one  turn.  Now  turn  the  armature  half  way 
round  and  wind  the  other  wire  in  the  same  way.  If  there 
are  to  be  more  turns,  continue  to  wind  the  second  turn. 
After  this  is  finished  turn  the  armature  back  to  its  original 
position  and  wind  the  first  wire  again.  Eepeat  in  this 
manner  until  the  desired  number  of  turns  in  both  coils  have 
been  obtained.  By  reference  to  Fig.  539  we  note  that  the 
windings  do  not  skip  slots  as  in  Fig.  534.  This  is  easily 
explained  when  it  is  noticed  that  each  slot  contains  two 
conductors  and  that  at  each  step  we  skip  one  conductor  as 
before. 

It  is  not  necessary  in  actual  practice  to  turn  the  arma- 
ture around  as  above  suggested.  This  was  suggested  merely 
as  a  beginning  to  make  the  principle  more  plain.  The 
same  result  can  readily  be  obtained  if  the  armature  is  left 
stationary.  The  windings  need  merely  to  be  so  arranged 
that  they  will  come  right  for  connection  to  the  commutator 
as  shown  in  the  cut. 

It  is  well  enough  to  use  care  that  all  of  the  coils  are  wound 
in  the  same  direction,  but  it  will  not  materially  affect  the 
operation,  if  one  part  of  the  coils  are  wound  left  hand,  and 
the  others  right  hand.  The  essential  point  is  to  see  that 
they  are  so  connected  that  the  magnetism  resulting  from  a 
current  flow  through  the  coil  will  be  the  same  in  all.  If 
it  is  different  in  one  coil  from  the  others  it  can  easily  be 
rectified  by  simply  changing  the  end  connections  of  the 
coil  in  question. 

864.    Are  all  armatures  hand  wound  ? 


142 


Steam  Engineering 


Ans.  Hand  winding  is  customary  with  the  smaller 
drum,  and  ring  armatures  only.  It  is  the  only  method 
that  can  be  used  with  ring  armatures,  and  also  with  drum 
armatures  where  the  wire  is  to  encircle  the  whole  armature. 
The  larger  dynamos  are  now  made  mostly  multipolar,  and 
in  these  the  coils  do  not  return  at  nearly,  or  wholly,  diam- 
etrically opposite  points  as  they  do  in  those  machines  we 
have  so  far  had  under  consideration.  With  multipolar  ma- 
chines the  armature  is  divided  into  as  many  sections  as 
there  are  poles.  While  it  is  possible  to  work  any  regularly 


FIG.  540 

wound  drum,  or  ring  armature  in  connection  with  many 
poles,  it  is  not  customary  to  do  so.  In  general  the  coil 
wound  on  a  multipolar  armature  has  its  return  winding 
spaced  about  as  far  from  the  first  turn,  as  it  is  from  the 
center  of  one  pole  piece  to  the  center  of  the  next  one. 

865.     How  does  this  affect  the  winding  ? 

Ans.  This  gives  us  a  winding  of  much  lower  resistance 
than  could  otherwise  be  obtained,  and  the  magnetic  circuit 
is  also  much  better.  Furthermore,  it  makes  possible  the 
use  of  so-called  "former  coils." 


Armature  Winding 


143 


866.  What  is  a  former  coil? 

Ans.  A  former  coil  is  one  that  is  wound  upon  a  former, 
i.  e.,  one  that  is  wound  complete  before  it  is  placed  upon  the 
armature. 

867.  How  are  such  coils  made  up  ? 

Ans.  Figs.  540  and  541  show  two  styles  of  former  coils, 
and  the  manner  in  which  they  are  wound.  In  Fig.  540  the 
black  circles  represent  strong  pins  fastened  into  a  piece  of 


FIG.  541 

plank,  or  other  suitable  material.  The  wire  is  wound 
around  these  pins  as  indicated  in  the  figure,  as  many  turns 
being  taken  as  it  has  been  decided  to  allow  for  each  coil. 
When  the  coil  is  thus  completely  wound  it  is  taken  from 
the  pins,  and  the  lower  ends  placed  in  a  suitable  clamp,  as 
indicated  by  the  broken  line  in  the  lower  center  of  the 
figure.  After  this  clamp  is  fastened  onto  the  coil  the  two 
halves  of  the  coil  are  spread  apart,  one  being  pulled  to- 
ward the  operator  and  the  other  pushed  away  from  him  at 


144  Steam  Engineering 

right  angles  to  the  clamp.  In  this  way  the  coil  is  made  to 
assume  the  shape  illustrated  in  Fig.  542.  Before  winding 
a  coil  in  this  manner  it  is  of  course  necessary  to  know  ex- 
actly what  length  it  must  be,  and  a  pattern  coil  must  there- 
fore first  of  all  be  prepared,  from  which  the  spacing  of  the 
pins  can  be  taken,  so  that  the  completed  coil  will  fit  into 
the  slots  for  which  it  is  intended. 

868.     How  are  such  coils  placed  upon  the  armature? 

Ans.  Begin  placing  the  coils  at  any  convenient  slot,  and 
lay  them  in,  as  indicated  in  Fig.  542.  It  is  necessary  to 
mark  the  beginning,  and  end  of  each  coil,  so  that  there 
may  be  no  wrong  connection  when  the  wires  are  finally 
connected  to  the  commutator. 


FIG.  542 


Before  placing  the  coils  the  slots  must  of  course  be  in- 
sulated as  explained  previously.  We  now  continue  to  lay 
in  coils  until  the  whole  armature  is  full,  but  when  nearly 
full,  the  forward  ends  of  the  coils  we  are  placing  require 
to  be  brought  under  the  first  coils  put  in  place.  To  do 
this  it  is  merely  necessary  to  raise  up  the  first  six  coils, 
(in  this  case)  and  place  the  forward  ends  of  i:he  last  six 
under  them  in  the  regular  order. 

869.     By  what  name  is  this  winding  known? 

Ans.  This  is  known  as  the  "e volute"  winding.  It  will 
be  noticed  that  when  this  winding  is  completed,  the  wires 
of  the  outer  portion  entirely  conceal  those  of  the  inner,  and 
thus  give  this  style  of  winding  its  characteristic  appearance. 


Armature  Winding  145 

870.  What  other  manner  of  winding  nmltipolar  arma- 
tures is  there? 

Ans.  Another  method  of  forming  coils  is  illustrated  in 
Fig.  541.  In  this  case  the  coil  is  first  wound  around  two 
pins,  as  shown  at  the  top  of  the  figure.  The  ends  are  then 
placed  in  clamps,  as  indicated  by  the  dotted  lines  at  the 
top  and  shaded  lines  in  the  center  of  the  figure.  After 
these  clamps  are  fastened,  the  coil  is  turned  one-fourth 
around,  and  the  wires  spread  over  the  four  pins,  as  indi- 
cated in  the  figure. 

871.  How  is  this  coil  placed  upon  the  armature? 


FIG.  543 

Ans.  The  coil  formed  in  the  manner  above  assumes  the 
shape  shown  in  side  view  in  Fig.  543  and  is  placed  upon 
the  armature  as  there  indicated,  the  manner  of  placing 
being  the  same  as  that  of  the  previous  coil. 

872.  What  name  is  given  to  this  style  of  winding? 
Ans.     This  is  termed  a  "barrel"  winding  and  its  charac- 
teristic appearance  can  be  seen  from  the  figure. 

873.  Is  it  necessary  to  carry  out  the  same  kind  of  wind- 
ing on  both  sides  of  an  armature? 

Ans.  There  is  nothing  to  prevent  one  from  using  one 
of  these  windings  on  one  side  of  the  armature,  and  the 
other  on  the  opposite  side.  They  cannot,  however,  be  com- 
bined on  the  same  side.  The  windings  of  large  machines 
very  often  are  made  up  of  bars  of  copper  made  of  special 


146 


Steam  Engineering 


sizes  to  suit.  These  are  often  arranged  as  shown  in  Figs. 
544  and  545.  Sometimes  such  bars  are  bare  and  laid  into 
the  slots  with  insulation  loose  on  the  sides  and  bottom  and 
between  the  different  bars  of  a  slot.  Such  winding  is  often 
held  in  place  by  pieces  of  wood  inserted  into  the  slots  as 
indicated  in  Eig.  543,  the  slots  being  specially  prepared  to 
admit  of  this.  Where  no  such  provision  has  been  made  the 
wires  are  held  in  place  by  the  usual  binding  wires. 

874.     Is  there  any  difference  between  the  armature  of 
motors  and  dynamos? 


FIG.  544 
MOTOR  ARMATURES. 

Ans.  Theoretically  there  is  no  difference  between  the 
armature  of  a  dynamo  and  motor.  In  fact,  many  machines 
are  placed  in  conditions  in  which  their  functions  change, 
perhaps  a  hundred  times  per  day,  from  that  of  generator 
to  that  of  motor. 

875.  Are  there  any  special  provisions  necessary  to  make 
them  operate  thus  ? 

Ans.  No.  This  change  takes  place  automatically,  and 
the  operation  is  so  smooth  that  the  observer  will  have  no 
idea  in  which  capacity  the  machine  may  be  operating  from 
moment  to  moment.  It  is  also  no  unusual  thing  for  a 
dynamo  working  in  parallel  with  other  generators  to  be- 


Armature  Winding  147 

come  reversed,  and  instead  of  delivering  current  to  the 
line,  it  will  be  drawing  from  it  and  running  as  a  motor. 

876.  What  should  one  principally  have  ia  view  in  the 
design  of  a  motor  armature  ? 

Ans.  Motor  armatures  must  be  designed  to  produce  a 
certain  counter  E.  M.  F.  just  as  dynamo  armatures  are 
designed  to  produce  E.  M.  F.  In  the  case  of  a  dynamo  the 
power  is  measured  by  the  product  of  the  E.  M.  F.  and  the 
current,  so  in  the  motor  the  power  is  proportional  to  the 
product  of  the  counter  E.  M.  F.  and  the  current. 


FIG.  545 

877.  How  do  you  proceed  to  calculate  the  winding  for 
a  motor  armature? 

Ans.    In  the  same  way  as  with  a  dynamo  except  that 
the  E.  M.  F.  should  not  be  figured  as  high.    The  current 

V-v 

passing  through  a  D.  C.  motor  equals ,  where  V  is  the 

R 

volume  of  the  line  that  supplies  it ;  v  the  counter  E.  M.  F. 
of  the  armature,  and  R  its  resistance.  It  is  apparent  that 
in  order  to  get  more  power  out  of  a  given  motor,  its  coun- 
ter E.  M.  F.  must  be  reduced  in  order  that  a  greater  cur- 
rent can  flow. 

878.  How  is  this  brought  about? 


148  Steam  Engineering 

Ans.  With  a  motor  in  operation  this  counter  E.  M.  F. 
is  reduced  when  the  speed  reduces,  on  account  of  a  heavier 
load.  More  current  is  thus  allowed  to  flow  until  the  power 
of  the  motor  becomes  equal  to  the  work  required  of  it,  but 
if  the  load  exceeds  the  capacity  of  the  motor  it  will  take 
too  much  current,  and  burn  out  the  armature.  If  a  motor 
is  to  be  designed  to  operate  at  a  certain  speed,  all  of  these 
facts  must  be  taken  into  consideration,  and  the  wires  so 
selected  that  when  running  at  the  required  speed,  the  neces- 
sary counter  E.  M.  F.  will  be  generated. 

For  illustration,  take  the  same  armature  that  was  con- 
sidered in  the  previous  section.  In  this  case  a  No.  12  wire 
was  required.  This  gave  11  turns  per  inch,  and  its  car- 
rying capacity  was  14.3  amperes.  The  dimensions  of  the 
armature  were  8"x8",  requiring  about  770  feet  of  wire. 
With  this  quantity  of  No.  12  the  resistance  is  1.39  ohms. 

Only  one-half  of  this,  however,  is  on  one  side,  and  only 
14.3  amperes  pass  on  one  side,  so  that  the  total  E.  M.  F. 
to  drive  this  current  through  the  armature  is  14.3X-697, 
which  is  9.96.  In  order  that  this  motor  may  allow  the  14.3 
amperes  to  pass,  its  counter  E.  M.  F.  must  fall  to  9.96 
volts  less  than  the  E.  M.  F.  of  the  line.  If  this  is  110,  the 
speed  must  slack  off  about  9  per  cent  in  order  that  the 
motor  may  develop  its  full  power. 

It  is  easily  seen  from  this  that,  in  order  that  the  motor 
may  operate  at  a  fairly  constant  speed,  the  resistance  of  the 
armature  should  be  made  as  low  as  possible.  In  practice  it 
is  generally  made  so  low  that  a  reduction  of  1  per  cent  in 
speed  wll  bring  about  the  required  lowering  of  counter 
E.  M.  F.  to  cause  the  proper  current  to  flow. 

879.     How  do  armature  troubles  manifest  themselves? 

Ans.  Either  by  excessive  sparking  at  the  commutator, 
or  by  abnormal  heating  of  the  armature. 


Armature  Troubles 


149 


880.    What  are  the  causes  of  such  troubles? 

Ans.  They  may  result  from  any  one  of  the  following 
causes :  There  may  be  a  wrong  connection  of  one,  or  more 
of  the  coils.  Some  of  the  coils  may  be  grounded.  There 
may  be  an  open  circuit.  There  may  be  a  short  circuit. 
The  brushes  may  be  improperly  set.  The  brushes  may  not 
make  sufficient  contact  with  the  commutator.  The  com- 
mutator may  be  rough  or  worn.  The  fields  may  be  of 
uneven  strength. 


FIG.  546 

881.  How  can  a  wrong  connection  of  the  coils  be  tested 
for? 

Ans.  In  order  to  see  how  this  test  can  be  made  let  us 
consider  Fig.  546  for  a  moment.  This  figure  shows  the 
wiring  of  an  armature  connected  to  the  commutator  seg- 
ments exactly  as  it  would  be  if  it  were  taken  off,  and  the 
coils  separated  without  detaching  from  the  commutator,  in- 
stead of  being  placed  in  an  orderly  manner  upon  the  core 
of  the  armature.  In  other  words,  the  connections  are  ex- 
actly as  in  an  armature.  If  we  should  now  take  the  two 


150  Steam  Engineering 

wires  of  some  supply  of  current  capable  of  delivering  a 
few  amperes,  and  connect  these  two  wires  to  two  adjacent 
commutator  segments,  as  shown  at  a,  and  b,  it  is  clear  that 
current  would  flow  through  the  coil  connected  between 
these  two  sections,  and  also  through  the  other  coils.  The 
current  has  two  paths:  one  through  the  single  coil,  the 
other  through  the  remaining  seven  coils  in  series. 

The  current  in  the  two  coils  flows  in  opposite  directions, 
with  the  result  that  a  field  of  force  is  set  up  in  the  vicinity 
of  the  single  coil.  A  suitable  galvanometer  placed  at  this 
point  will  be  deflected  in  a  certain  direction.  By  revolving 
the  armature  and  applying  the  test  to  each  succeeding  pair 
of  commutator  sections,  a  number  of  deflections  of  the 
needle  will  be  obtained. 

If  all  the  coils  are  correctly  connected  these  deflections 
will  all  be  in  the  same  direction.  If  one  of  the  coils  is  con- 
nected wrong,  a  different  deflection  will  be  obtained.  If 
one  of  the  coils  has  been  wound  on  in  the  wrong  direction, 
it  is  not  necessary  to  rewind  it ;  the  connections  can  simply 
be  reversed. 

882.  What  is  meant  by  a  "ground"  ? 

Ans.  An  electrical  connection  between  some  current 
carrying  part  of  the  armature,  and  the  metal  armature 
frame.  A  "ground"  is  often  caused  by  the  insulating  cov- 
ering of  the  wire  breaking  down,  thus  allowing  the  wire  to 
come  in  contact  with  the  iron  core. 

883.  How  do  you  test  for  this  condition? 

Ans.  The  simplest  method  of  testing  for  a  ground  con- 
sists in  taking  a  lamp  or  voltmeter  and  connecting  it  as 
shown  in  Fig.  546.  Place  one  of  the  wires  in  contact  with 
the  iron  core,  and  the  other  in  contact  with  the  wire  on 
the  armature.  If  the  lamp  lights,  there  is  a  connection  be- 
tween the  wire  and  the  core,  and  this  should  be  removed. 


Armature  Troubles  151 

884.  How  is  an  open  circuit  located  ? 

Ans.  Referring  to  Fig.  546,  connect  the  commutator 
as  shown  by  the  horizontal  lines  c.  d.  to  some  source  of 
supply.  A  rheostat  is  needed  to  adjust  the  current  strength 
until  a  suitable  deflection  of  the  needle  is  obtained  between 
adjacent  commutator  segments.  Now,  take  two  wires  of 
the  voltmeter  and  test  the  voltage  between  the  various  ad- 
jacent commutator  segments.  A  reading  will  be  obtained 
between  each  two  segments  on  one  side  of  the  commutator, 
but  on  the  side  which  contains  the  open  coil  no  reading 
will  be  obtained  until  connection  is  made  between  the  two 
segments  to  which  the  open  coil  is  connected.  At  this 
point  the  voltmeter  will  show  practically  the  full  voltage  of 
the  supply  current. 

885.  How  do  you  locate  a  short  circuit? 

Ans.  If  the  short  circuit  has  come  on  while  the  arma- 
ture was  in  use,  it  will  locate  itself  by  a  burned  out  coil. 
To  test  a  new  armature  for  short  circuits  we  can  proceed 
in  the  same  way  as  for  open  circuit,  the  only  difference 
being  that,  when  we  come  to  the  short-circuited  coil,  we 
shall  obtain  either  none,  or  at  least  a  reduced  deflection. 

886.  What   effect  does  an   improper  location   of  the 
brushes  have? 

Ans.  An  improper  location  of  the  brushes  will  mani- 
fest itself  by  a  more  or  less  severe  sparking.  If  the  brushes 
are  of  the  right  dimensions  the  trouble  can  be  remedied 
by  simply  shifting  them  to  the  proper  location,  which  is  that 
of  least  sparking.  Brushes  should  be  of  such  length,  and 
set  at  such  an  angle,  that  they  come  in  contact  with  diamet- 
rically opposite  points  on  the  commutator,  with  all  bi-polar 
machines. 

887.  How  must  the  brushes  be  set  in  connection  with 
multipolar  machines  ? 


152  Steam  Engineering 

Ans.  This  depends  on  the  manner  in  which  the  armature 
is  wound.  With  a  lap  winding  there  are  as  many  brushes 
as  there  are  pole  pieces,  and  they  must  be  equally  spaced 
around  the  periphery  of  the  commutator.  Provision  must 
also  be  made  so  that  they  can  be  shifted  to  the  point  of  least 
sparking.  In  wave  wound  armatures  there  may  be  only 
two  brushes,  these  being  so  spaced  that  they  are  separated 
by  an  angle  equal  to  the  angle  of  separation  of  two  ad- 
jacent pole  pieces;  for  instance,  with  a  four-pole  field  they 
would  be  separated  by  an  angle  of  90°. 

888.  Is  much  shifting  of  the  brushes  necessary? 

Ans.  This  depends  very  much  on  the  design  of  the  ma- 
chine. With  some  of  the  older  machines  constant  shifting 
of  the  brushes  is  required  with  changes  in  the  load,  but  with 
the  newer,  and  better  machines  this  is  reduced  to  a  mini- 
mum. 

889.  What  is  the  ordinary  size  of  a  carbon  brush? 
Ans.     It  should  be  of  such  size  that  not  more  than  25 

to  40  amperes  per  square  inch  of  carbon  are  ever  required 
to  flow  through  it. 

890.  How  does  inequality  in  field  strength  affect  an  ar- 
mature ? 

Ans.  Wherever  this  exists  there  will  be  more  lines  of 
force  cut  by  the  armature  on  one  side  than  on  the  other, 
thus  causing  a  higher  potential  to  be  generated  on  one  side 
than  on  the  other.  The  brushes  will  have  to  be  set  uneven 
distances  apart  around  the  commutator,  and  useless  cur- 
rents will  be  set  up  in  the  armature  windings,  which  will 
not  only  cause  a  loss  of  power,  but  which  will  tend  to  over- 
heat the  armature. 


Transformers 


891.  What  is  the  function  of  a  transformer? 

Ans.  To  transform  the  current  from  a  higher,  to  a  lower 
voltage,  or  vice-versa. 

892.  What  principles  govern  the   action   of  a  trans- 
former ? 

Ans.     The  principles  of  electro-magnetic  induction. 

893.  What  is  a  step  up  transformer? 
Ans.     A  transformer  that  raises  the  voltage. 

894.  What  is  a  step  down  transformer? 
Ans.     One  that  lowers  the  voltage. 

895.  How  are  transformers  cooled? 

Ans.  Small  sizes  by  surface  radiation.  Larger  sizes  by 
oil;  also  by  air  blast.  Some  of  the  smaller  sizes  are  cooled 
by  water  circulating  through  surrounding  coils. 

896.  How  is  direct  current  transformed  from  one  volt- 
age to  another  ? 

Ans.    By  means  of  a  machine  called  a  motor-generator. 

897.  Describe  in  brief  a  motor-generator. 

Ans.  It  consists  usually  of  a  D.  C.  motor  driven  by 
current  at  the  voltage  of  the  incoming  line.  This  motor  in 
turn  drives  a  D.  C.  generator  that  furnishes  current  at  the 
desired  voltage. 

898.  How  is  the  outgoing  voltage  regulated? 

Ans.     By  altering  the  field  strength  of  the  generator. 

899.  In  case  the  incoming  and  outgoing  current  can  bear 
the  same  ratio  to  each  other  constantly,  what  kind  of  an 
apparatus  is  used  ? 

Ans.    A  machine  called  a  dynamotor. 
153 


154  Steam  Engineering 

900.  Describe  the  operation  of  a  dynamotor. 

Ans.  It  is  a  D.  C.  motor  running  on  the  incoming  volt- 
ages. On  the  same  armature  core  is  a  separate  winding 
connected  to  its  own  commutator  at  the  other  end  of  the 
armature.  One  set  of  field  magnets  serves  for  the  motor 
winding  and  the  generator  or  dynamo  winding. 

901.  Describe  in  general  terms  a  rotary  converter. 

Ans.  It  combines  in  a  single  machine  the  functions  of 
a  motor-generator,  and  a  dynamotor. 

902.  Why  are  rotary  converters  and  transformers  neces- 
sary? 

Ans.  Because  it  is  more  economical  to  transmit  alter- 
nating current  at  high  voltages  and  transform,  or  convert 
it  to  the  lower  voltage  at  which  it  is  used. 

903.  Give  another  reason  for  using  rotary  converters. 
Ans.    For  the  purpose  of  transforming  alternating  cur- 
rent into  direct  current  when  direct  current  is  used. 

904.  What  is  the  chief  point  of  difference  between  a 
rotary  converter  and  a  direct  current  generator? 

Ans.  The  rotary  has  collector  rings  connected  to  certain 
points  of  the  armature  winding. 

905.  What  governs  the  number  of  such  connections  ? 
Ans.    The  number  of  poles  and  phases. 

906.  Describe  the  different  types  of  rotaries. 

Ans.  They  are  built  for  single-phase,  two-phase,  three- 
phase  or  six-phase. 

907.  How  many  collecting  rings  has  a  two-phase  con- 
verter? 

Ans.    Four  collecting  rings. 

908.  How  many  collecting  rings  has  a  three-phase  con- 
verter ? 

Ans.    Three  collecting  rings. 


Hotary  Converters  155 

909.  When  alternating  current  is  transmitted  at  high 
pressure,  what  means  are  employed  for  lowering  the  po- 
tential? 

Ans.     Transformers. 

910.  When  the  incoming  current  is  direct  and  the  out- 
going current  alternating,  how  is  the  voltage  raised? 

Ans.     By  step  up  transformers. 

911.  Describe  the  winding  of  a  rotary  converter. 

Ans.  It  is  usually  shunt  wound,  or  compound  wound, 
although  sometimes  separately  excited. 

912.  How  are  rotaries  in  railway  service  usually  wound  ? 
Ans.     Compound,  owing  to  variations  in  the  load. 

913.  What  advantage  is  gained  by  this  method  of  wind- 
ing? 

Ans.    It  tends  to  maintain  the  D.  C.  voltage  constant. 

914.  Upon  what  does  the  ratio  between  the  A.  C.  and 
D.  C.  voltages  of  a  rotary  depend  ? 

Ans.  Upon  the  number  of  phases,  the  lead  given  the 
D.  C.  brushes,  the  wave  form  of  its  alternating  current, 
and  upon  the  field  excitation. 

915.  Does  the  armature  drop  affect  this  ratio  to  any 
extent? 

Ans.  It  does  by  decreasing  it  slightly  when  running 
A.  C.  to  D.  C.  and  increasing  it  when  running  D.  C.  to 
A.  C. 

916.  What  are  the  ratios  of  conversion  approximately? 
Ans.     Single-phase 71 

Two-phase 71 

Three-phase 61 

Six-phase 71  or  .61 

917.  Give  an  example  illustrating  above. 


156  Steam  Engineering 

Ans.  If  D.  C.  voltage  is  550  volts,  the  A.  C.,  if  two- 
phase  will  be  500X-71=390  volts,  or  if  three-phase  it  will 
be  550 X- 61=335  volts. 

918.  What  precautions  should  be  observed  in  the  erec- 
tion of  a  rotary  converter? 

Ans.  First — It  should  be  protected  from  moisture.  Sec- 
ond— It  should  be  protected  from  dust  or  dirt.  Third — It 
should  be  in  a  well  ventilated  room  and  kept  as  cool  as 
possible. 

919.  Should  the  frame  of  the  machine  be  insulated? 

Ans.  Generally  speaking  the  strain  on  the  winding  in- 
sulation will  be  decreased,  and  danger  to  attendant  increased 
by  insulating  the  frame. 

920.  If  a  rotary  has  been  exposed  to  dampness  how  may 
it  be  dried  out? 

Ans.  By  running  it  with  about  10  per  cent  of  the  nor- 
mal A.  C.  voltage,  while  at  same  time  'observing  certain 
precautions  noted  in  the  text  of  this  book  under  head  of 
rotary  converters. 

921.  What  method  should  be  pursued  in  caring  for  the 
commutator  ? 

Ans.  Wipe  it  off  with  a  piece  of  canvas — never  use  waste. 
Lubricate  it  with  a  very  small  quantity  of  vaseline,  or  oil 
applied  with  a  piece  of  cloth.  See  that  none  of  the  segments 
is  at  all  loose. 

If  it  gets  out  of  true  turn  it  down. 

922.  If  a  commutator  gets  hot  while  carrying  only  a 
normal  load  what  should  be  done  ? 

Ans.  Heating  under  such  conditions  is  an  indication 
that  the  commutator  is  worn  out,  and  should  be  replaced 
by  a  new  one. 

923.  Give  some  of  the  causes  of  sparking  at  the  brushes. 


The  Commutator  157 

Ans.     Brushes  may  not  have  proper  lead. 
Brushes  may  not  fit  commutator. 
Brushes  may  be  burned  on  end. 
Commutator  surface  may  be  rough. 

924.  What  is  meant  by  a  rotary  bucking? 

Ans.  When  arcing  occurs  between  two  adjacent  brush 
holder  arms,  thus  short  circuiting  the  machine. 

925.  Name  a  few  of  the  principal  causes  of  bucking. 
Ans.     Rough  or  dirty  commutator. 

Excessive  voltage. 
Fluctuations  in  the  voltage. 

926.  What  is  an  oscillator,  and  what  is  its  function  ? 

Ans.  An  oscillator  is  a  device  operated  either  magnet- 
ically, or  by  mechanical  means,  and  its  function  is  to  pro- 
duce a  slight,  periodic  movement  of  the  armature  shaft 
endwise. 

927.  Why  is  this  endwise  movement  of  the  shaft  neces- 
sary? 

Ans.  In  order  to  prevent  the  wearing  of  grooves  in  the 
commutator. 

928.  What  is  meant  by  the  hunting  of  a  rotary  con- 
verter ? 

Ans.    It  is  a  slight  change  of  the  speed  of  the  armature. 

929.  What  is  the  cause  of  hunting? 

Ans.  Irregularities  in  the  speed  of  the  generator  deliv- 
ering current  to  the  rotary,  thus  causing  a  slight  difference 
in  the  relative  positions  of  the  armature  of  the  two  machines, 
resulting  in  a  change  in  the  phase  positions  of  the  generator 
E.  M.  F.  and  the  counter  E.  M.  F.  of  the  converter. 

930.  What  are  the  usual  methods  of  starting  rotary  con- 
verters ? 

Ans.    First — By  a  separate  A.  C.  starting  motor. 


158  Steam  Engineering 

Second — By  applying  direct  current  to  the  commutator. 
This  starts  the  converter  as  a  shunt  motor. 

Third— By  applying  alternating  current  directly  to  the 
collector  rings.  This  starts  the  converter  as  an  induction 
motor. 

931.  What  is  meant  by  synchronizing  a  rotary  converter  ? 
Ans.     Bringing  it  to  the  same  frequency,  the  same  phase, 

and  the  same  voltage  as  the  generator  from  which  it  is 
receiving  current. 

932.  What  method  is  employed  to  determine  when  the 
machines  are  in  synchronism  ? 

Ans.  There  are  several  methods,  the  most  common  one 
being  by  means  of  incandescent  lamps  connected  in  series 
with  the  two  machines. 

933.  What  is  a  synchroscope? 

Ans.  It  is  an  instrument  for  determining  when  electrical 
machines  are  in  synchronism. 

934.  What  is  an  automatic  synchronizer? 

Ans.  It  is  a  device  that  will  automatically  synchronize 
two  electrical  machines;  also  connect  a  synchronized  ma- 
chine with  the  main  by  means  of  an  electrically  operated 
switch. 

935.  Name  two  important  points  to  be  looked  after  be- 
fore starting  a  rotary  converter. 

Ans.  First — See  that  both  the  A.  C.  and  D.  C.  brushes 
are  properly  adjusted  and  that  every  thing  is  clear  about 
the  converter.  Second — See  that  the  switches  on  board  are 
open  on  both  the  A.  C.  and  D.  C.  sides,  and  that  the  resist- 
ance of  the  rheostat  is  all  cut  in  the  field  circuit. 


Switch  Boards 


935.  How  are  switchboards  made  up? 

Ans.  They  are  built  up  of  panels  of  slate  or  marble  sup- 
ported by  frames  of  angle  iron. 

936.  How  are  the  different  panels  designated  ? 

Ans.  Some  are  for  motor  control,  others  for  dynamo 
running,  others  for  operating  the  outer  circuit,  and  others 
for  charging  storage  batteries. 

937.  Is  a  knowledge  of  switchboards  an  important  mat- 
ter? 

Ans.  It  is,  and  every  engineer  should  especially  study 
those  in  his  own  station. 

938.  What  is  the  regular  equipment  of  a  D.  C.  switch- 
board having  a  capacity  of  from  250  to  6,500  amperes? 

Ans.  One  carbon-break  or  magnetic  blow-out  circuit 
breaker  with  telltale. 

One  illuminated  dial  ammeter  with  shunt.  , 
One  hand  wheel  and  chain  for  operating  rheostat. 
One  receptacle  for  voltmeter  plug. 
One  S.  P.  S.  T.  field  switch. 
One  S.  P.  S.  T.  main  switch. 
One  recording  watt-hour  meter. 

939.  What  is  meant  by  the  abbreviations  S.  P.  S.  T.?. 
Ans.     Single  Pole  Single  Throw. 

940.  What  does  D.  P.  D.  T.  mean  in  speaking  of  switch- 
boards ? 

Ans.     Double  Pole  Double  Throw. 

941.  What  is  meant  by  T.  P.? 

159 


160  Steam  Engineering 

Ans.  Triple  pole.  It  opens  every  circuit  of  a  three- 
phase  system. 

943.  Is  it  good  practice  to  place  a  main  switch  at  the 
machine? 

Ans.    It  is  best. 

943.  Why? 

Ans.  So  that  the  cables  from  generator  to  board  may 
be  cut  off  at  the  generator. 

944.  What  is  an  equalizer? 

Ans.  It  is  a  cable  running  along  from  machine  to  ma- 
chine, and  connecting  the  functions  of  series  field  and 
brush  on  all  the  machines,  but  does  not  connect  with  switch- 
board. 

945.  What  kind  of  a  break  has  the  field  switch? 
Ans.    A  carbon  break. 

946.  Describe  the  action  of  a  field  switch. 

Ans.  Just  before  it  opens  it  makes  contact  with  an  extra 
clip,  and  puts  a  resistance  on  as  a  shunt  around  the  field 
coils. 

947.  If  this  were  not  done  what  would  be  the  conse- 
quences ? 

Ans.  The  fields  would  act  as  a  spark-coil  and  the  in- 
sulation be  damaged. 

948.  When  it  is  desired  to  throw  a  generator  in  par- 
allel with  other  generators  already  running  what  is  the 
proper  method  of  procedure? 

Ans.  First.  Close  main  and  equalizer  switches  near  the 
machine. 

Second.    Close  field  switch  on  panel. 

Third.    Close  circuit  breaker. 

Fourth.  Insert  potential  plug  in  receptacle  and  regulate 
voltage. 


Switchboards 


161 


Fifth.    When  proper  voltage  is  obtained  close  the  other 
main  switch  on  panel. 

949.  What  is  meant  by  voltage? 
Ans.     Electric  pressure,  or  potential. 

950.  What  is  a  volt? 
Ans.     The  unit  of  pressure. 

951.  What  is  a  voltmeter? 

Ans.    An  instrument  that  indicates  the  voltage. 

952.  What  is  an  ohm? 
Ans.     The  unit  of  resistance. 

953.  Give  a  brief  definition  of  Ohm's  law? 

Ans.    The  electromotive  force  equals  the  resistance  mul- 
iplied  by  current  intensity. 

954.  What  is  an  ampere? 

Ans.     It  is  the  unit  of  volume,  or  quantity-time  unit  for 
easuring  the  rate  of  flow  of  an  electric  current. 

955.  What  is  a  coulomb? 

Ans.     It  is  an  ampere-second.     A  coulomb  equals  the 
ow  of  an  ampere  of  current  past  a  given  point  each  second 
time. 

956.  What  is  an  ammeter? 

Ans.     An  apparatus  for  measuring  current  rate. 

957.  What  is  the  meaning  of  the  word  watt  as  used 
electrical  work? 

Ans.    A  watt  is  the  unit  of  work.    It  equals  volts Xan> 

958.  What  is  the  function  of  the  wattmeter? 
Ans.  To  record  the  watt-hours  of  work. 

959.  What  is  a  kilo  watt  (K.  W.)  ? 
Ans.  1,000  watts. 

960.  Expressed  in  horse-power,  what  is  one  K.  W.  equal 


162  Steam  Engineering 

Ans.     746  horse-power. 

961.  What  is  a  field  rheostat? 

Ans.     An  apparatus  for  controlling  the  current  output. 

962.  What  is  the  function  of  a  transformer? 

Ans.  To  transform  the  current  from  a  higher  to  a  lower 
voltage,  or  from  A.  C.  to  D.  C. 

963.  What  is  meant  by  synchronism  of  electric  ma- 
chines ? 

Ans.  When  the  maximum  value  of  the  E.  M.  F.  in 
each  machine  occurs  at  exactly  the  same  instant  of  time, 
the  machines  are  in  synchronism. 

964.  What  is  meant  by  the  exciter  panel  of  a  switch- 
board ? 

Ans.  It  is  the  panel  that  is  equipped  with  the  necessary 
switches,  etc.,  for  connecting  the  small  exciter  dynamo  with 
the  other  generators  in  the  station. 

965.  What  is  a  sub-station? 

Ans.  It  is  the  connecting  link  between  the  transmission 
line,  and  the  trolley  wire  or  third  rail. 

966.  When  A.  C.  is  generated  at  the  power  station,  and 
D.  C.  is  used  on  the  line,  how  is  it  accomplished  ? 

Ans.  The  A.  C.  is  changed  to  D.  C.  by  rotary  converters 
at  the  sub-station. 

967.  What  is  meant  by  frequency? 

Ans.  The  number  of  times  the  current  reverses  per  sec- 
ond. 

968.  What  is  the  usual  frequency  for  railway  motors? 
Ans.  25  is  the  standard. 

969.  What  is  a  frequency  changer? 

Ans.  A  machine  which  receives  current  at  one  frequency 
and  delivers  it  at  another  frequency. 

970.  What  apparatus  is  used  in  an  A.  C.  to  D.  C.  sub- 
station ? 


Switchboards  163 

Ans.  Step  down  transformers,  rotary  converters,  and 
A.  C.  incoming  and  D.  C.  outgoing  switchboards. 

971.  What  is  the  proper  procedure  for  placing  rotary 
converters  in  service? 

Ans.  After  the  machine  .has  been  started  from  the  A. 
C.  ends,  and  builds  up  with  the  proper  polarity,  first  close 
the  equalizer  switch  (on  machine) — second,  close  circuit 
breaker  on  panel — third,  insert  potential  plug  in  receptacle 
and  regulate  voltage — fourth,  when  the  proper  voltage  is 
obtained,  close  positive  switch  (on  panel). 

972.  What  will  be  the  result  if  the  rotary  builds  up  with 
polarity  reversed? 

Ans.     The  voltmeter  will  swing  back  of  zero. 

973.  How  may  the  polarity  be  corrected  ? 

Ans.  By  means  of  the  four-pole,  double-throw  field 
break-up  reversing  switch  mounted  on  the  converter. 

974.  Describe  an  oil  switch. 

Ans.  It  is  a  switch  similar  in  its  action  to  other 
switches,  with  the  exception  that  its  mechanism  is  im- 
mersed in  a  small  tank  of  oil. 

975.  What  advantage  is  gained  thereby? 

Ans.  Eeliability  of  action  in  opening  or  closing  a  cir- 
cuit. 

976.  Mention  another  advantage  gained  by  the  use  of 
the  oil  switch  and  oil  circuit  breaker. 

Ans.  It  has  made  safely  possible  the  transmission  and 
use  of  high-tension  currents  of  electricity. 

977.  What  is  a  circuit  breaker? 

Ans.  It  is  a  switch  so  designed  as  to  be  capable  of  fre- 
quently opening  the  circuit  carrying  its  full  current  with- 
out any  damage  to  itself. 

978.  What  is  a  galvanometer? 


164  Steam  Engineering 

Ans.  An  instrument  consisting  of  a  coil  of  wire  car- 
rying the  current  to  be  tested,  and  a  magnet,  the  two  be- 
ing arranged  so  that  one  can  be  deflected. 

979.  Describe  the  Thompson  type  of  galvanometer. 
Ans.    The  coil  of  wire  is  stationary,  and  the  light  mag- 
netic needle  is  suspended  by  a  silk  thread. 

980.  What  is  a  lightning  discharge? 

Ans.  An  equalization  of  potential  between  the  earth, 
and  either  clouds,  or  saturated  atmosphere. 

981.  What  path  does  the  discharge  generally  follow  ? 
.    Ans.    The  path  of  least  resistance. 

982.  What  are  the  general  requirements  for  protection 
of  electric  stations  from  lightning? 

Ans.  The  supplying  of  paths  to  ground  for  any  charge 
which  might  accumulate  on  lines  or  machinery. 

983.  What  is  the  general  theory  of  the  multi-gap  light- 
ning arrester? 

Ans.  When  voltage  is  applied  across  a  series  of  multi- 
gap  cylinders,  the  voltage  distribution  is  not  uniform,  but 
is  governed  by  the  capacity  of  the  cylinders,  both  between 
themselves,  and  also  to  ground,  which  results  in  the  con- 
centration of  voltage  across  those  gaps  nearest  the  line. 

984.  What  are  the  principal  elements  of  a  600  volt 
D.  C.  aluminum  lightning  arrester? 

Ans.  Two  concentric  aluminum  plates  immersed  in  an 
electrolyte  contained  in  a  glass  jar,  the  outside  plate  of 
each  cell  being  positive,  and  the  inner  one  negative. 

985.  Describe  the  multigap  lightning  arrester  for  A.  C. 
Ans.    It  consists  of  a  series  of  spark  gaps  shunted  by 

graded  resistances,  but  without  series  resistance. 

986.  Describe  briefly  the  aluminum  lightning  arrester. 


The  Galvanometer  165 

Ans.  It  consists  of  two  aluminum  plates  on  which  has 
been  formed  a  film  of  hydroxide  of  aluminum,  immersed 
in  a  suitable  electrolyte. 

987.  Describe  the  D'Arsonval  galvanometer. 

Ans.  In  this  type  the  small  light  coil  of  wire  is  sus- 
pended by  a  fine  bronze  wire  between  the  poles  of  a  station- 
ary magnet. 

988.  How  are  the  readings  taken  from  these  instru- 
ments ? 

Ans.  From  a  circular  scale,  over  which  the  needle  of 
the  instrument  swings. 


Definitions 


A.  C. — Alternating  Current. 

Absorption. — The  act  of  one  form  of  matter  sucking,  or 
draining  in  some  other  form  of  matter,  as  in  the  case 
of  a  sponge  taking  up  water. 

Acceleration. — The  increase  of  motion. 

Accumulated  Electricity. — Electricity  confined  or  stored, 

as  in  a  condenser. 

Accumulator. — Sometimes  used  to  designate  a  condenser,  a 
Ley  den  jar,  or  a  storage  battery. 

Active  Coil. — A  coil  or  conductor  conveying  a  current  of 
electricity. 

Active  Current. — The  active  constituent  of  an  alternating 
current,  in  contradistinction  from  the  wattless  compo- 
nent. 

Active  Wire. — The  section  of  wire  on  the  armature  of  a 
dynamo  which  goes  through  the  field  of  force,  in  con- 
tradistinction from  the  remaining  wire,  which  does  not 
pass  through  the  flux. 

Aerial  Circuit. — An  elevated  circuit. 

Air  Blast. — A  blast  of  air  acting  upon  the  surface  of  a 
commutator  to  prevent  damaging  flashes.  Also  used  to 
cool  transformers  in  some  cases. 

Air  Gap. — Any  gap  or  aperture  in  a  circuit  which  con- 
tains air  only. 

Air  Insulation. — Insulation  produced  by  the  action  of  air. 

167 


168  Steam  Engineering 

American  Wire  Gauge. — The  name  by  which  the  Brown  & 
Sharpe  wire  gauge  is  known,  in  which  the  diameter  of 
the  largest  wire,  No.  0000,  is  0.46  inches,  and  wire  No.  36, 
0.005  inches,  and  all  other  diameters  progress  in  geomet- 
rical order. 

Ammeter. — An  abbreviation  for  ampere  meter.  Used  for 
measuring  current  rate,  or  volume.  Any  calibrated  gal- 
vanometer having  its  scale  marked  to  read  amperes  is 
an  ammeter. 

Ampere. — The  unit  of  electric  current  flow.  An  ampere  is 
that  volume  of  current  which  would  pass  through  a  cir- 
cuit that  offered  a  resistance  of  one  ohm  under  an  electro- 
motive force  of  one  volt. 

Ampere  Hour. — A  unit  of  quantity  equal  to  the  amount  of 
electricity  transmitted  by  one  ampere  flowing  during  one 
hour. 

Ampere  Turn. — A  unit  of  magneto-motive  force  equal  to 
the  force  resulting  from  the  passing  of  one  ampere  over  a 
single  turn  of  wire. 

Anode. — The  positive  pole  a  battery. 

Arc. — A  segment  of  a  circle.    A  voltaic  arc. 

Armature  Reaction. — The  reactive  magnetic  effect  result- 
ing from  the  action  of  the  current  in  the  armature  of  a 
dynamo  on  the  magnetic  circuit  of  the  machine. 

B 

B.  S.  G. — British  standard  gauge. 

B.  &  S.  W.  G. — Brown  &  Sharpe  wire  gauge. 

B.  W.  G. — Birmingham  wire  gauge. 

Balanced  Load. — A  load  uniformly  apportioned  to  two  or 

more  generators. 
Balanced  Resistance. — A  resistance  arranged  in  a  bridge, 

and  balanced  by  the  residuary  resistance  in  the  bridge. 


Definitions  169 

Bar  Windings. — Armature  windings  constructed  of  copper 
bars. 

Bipolar. — Possessing  two  poles. 

Birmingham  Wire  Gauge. — A  wire  gauge  used  in  England. 

Booster. — An  auxiliary  dynamo  used  to  increase  the  volt- 
age of  a  feeder,  or  a  set  of  feeders  beyond  the  voltage  of 
the  rest  of  the  system. 

Bridge,  Electric. — A  contrivance  used  to  measure  unknown 
resistances  by  comparison  with  adjustable  ones. 

Bunched  Cable. — A  cable  having  more  than  one  wire,  or 
conductor. 

Bus-bars. — Bars  composed  of  heavy  conducting  metal,  and 
connected  directly  with  the  poles  of  generators. 

C 

C.  G.  S. — Centimetre,  Gramme,  second. 

C.  P. — Candle  power. 

Calibrate. — To  ascertain  the  complete  or  relative  values  of 
the  indications  of  electrical  measuring  instruments. 

Candle. — The  unit  of  photometric  energy.  Equals  the  light 
produced  by  a  standard  candle  burning  at  the  rate  of  two 
grains  per  minute. 

Cathode. — Opposed  to  anode. 

Condenser. — A  device  for  augmenting  the  capacity  of  an 
insulated  conductor  by  placing  it  in  contiguity  to  another 
earth-connected  conductor,  but  from  which  it  is  sep- 
arated by  an  intervening  body  which  will  permit  electro- 
static induction  to  occur  through  it. 

Constant  Current. — A  current,  the  strength  of  which  does 
not  vary. 

Continuous  Current. — A  current  flowing  in  the  same  di- 
rection only. 

Cycle  of  Alternations. — Alternations  of  the  current  per 

second. 


170  Steam  Engineering 

Coulomb. — The  unit  of  electric  quantity  accepted  for  prac- 
tice. That  quantity  of  electricity  that  would  pass  in  one 
second  through  a  circuit  conveying  one  ampere.  That 
quantity  of  electricity  contained  in  a  condenser  of  one 
Farad  capacity  when  subjected  to  an  E.  M.  F.  of  one 
volt. 

D. 

D.  C. — Direct  current. 

D.  P.  S. — Double  pole  switch. 

Differential  "Winding. — Double  winding  of  magnet  coils 
resulting  in  the  opposition  of  the  two  poles  to  each  other. 

Dynamic  Electricity. — Current  electricity  as  distinguished 
from  static  electricity. 

Dyne.— The  C.  G.  S.  unit  of  force. 

E 

E.  H.  P. — Electrical  horse-power. 
E.  M.  F. — Electromotive  force. 

Electrolysis. — Chemical  decomposition  by  the  action  of  an 
electric  current. 

F 

Farad. — The  practical  unit  of  electrical  capacity.  That 
capacity  of  a  conductor  that  is  capable  of  holding  one 
coulomb  at  one  volt  potential. 

Feeders. — Wires  furnishing  the  main  conductors  with  cur- 
rents at  different  points,  thus  serving  to  equalize  the  po- 
tential under  load. 

Five- wire  System. — A  system  wherein  four  series  connected 
dynamos  are  connected  to  five  conductors. 

Flux. — Magnetic  induction;  the  number  of  lines  of  force 
which  pass  through  a  magnetic  circuit. 

Frequency. — Number  of  cycles  per  unit  of  time  by  an  al- 
ternating current. 


Definitions  171 

G 

Gramme. — A  unit  of  weight  equal  to  the  weight  of  one  cubic 
centimetre  of  pure  water  at  its  maximum  density,  at  a 
temperature  of  39.2°   Fahr.  in  a  vacuum.     A  weight 
equal  to  15.44  grains  troy. 

H 

H.  P. — Horse-power. 

Hard-drawn  Copper  Wire. — Copper  wire  hardened  without 
annealing,  by  being  drawn  several  times. 

Henry. — The  practical  unit  of  electro-magnetic,  or  mag- 
netic inductance. 

Horse-power,  Electric. — A  rate  of  electrical  work  equal  to 
746  watts,  or  746  volt-coulombs  per  second. 

Hysteresis. — Slowness  of  magnetization  in  respect  to  mag- 
netizing force. 

I 

Induction. — The  influence  exerted  without  contact,  by  a 

magnetic   field,   or  a  charged  mass  upon,  neighboring 

bodies. 
Inverted  Arc  Lamp. — An  arc  lamp  wherein  the  positive 

carbon  is  below  instead  of  above,  as  in  the  regular  arc 

lamp. 

J 

Jump  Spark. — A  disruptive  spark  excited  between  two  con- 
ductors, in  distinction  from  a  spark  excited  by  a  rubbing 
contact. 

K 

K.  W.— Kilowatt. 
Kilowatt. — One  thousand  watts. 

Kilowatt-Hour. — Work  equal  to  the  expenditure  of  one  K. 
W.  in  one  hour. 


172  Steam  Engineering 

L 

Lag. — Dropping  behind. 

Lagging  of  Current. — The  retarding  in  phase  of  an  al- 
ternating current  behind  the  pressure  which  produces  it. 

M 

Megohm. — One  million  ohms. 

Metre. — A  measure  of  length  equal  to  39.368  inches. 

Micro-Fard. — The  millionth  of  a  Farad. 

Mil. — One  thousandth  of  an  inch. 

Multiphase. — Containing  more  than  one  phase. 

Multiple  Circuit. — A  circuit  in  which  the  positive  poles  of 
a  number  of  separate  sources,  and  receptive  devices  are 
connected  to  a  single  positive  lead  or  conductor;  their 
negative  poles  being  connected  to  a  single  negative  lead 
or  conductor. 

Multiple  Series. — Series  groups  connected  in  multiple. 

0 

Ohm. — The  practical  unit  of  resistance.  A  resistance  that 
would  confine  the  electric  flow  under  an  electromotive 
force  of  one  volt  to  a  current  of  one  ampere,  or  one  cou- 
lomb per  second. 

Ohm's  Law. — The  basic  law,  expressing  the  relation  be- 
tween current,  E.  M.  F.,  and  resistance  in  active  cir- 

E 

cuits.    Expressed  algebraically  1= — ,  in  which  I  equals 

R 

current  intensity,  E  equals  E.  M.  F.,  and  K  equals  resist- 
ance. Other  forms  of  expressing  ohms  law  are  as  follows : 

Bbs-H    E=BL 


Definitions  173 

Over  Compounded. — Compound  winding  of  such  a  charac- 
ter on  a  dynamo  that  its  voltage  at  its  terminals  is  caused 
to  increase  under  a  greater  load. 

P 

Parallel  Circuit. — A  term  signifying  multiple  circuit. 

Parallel  Series. — Signifies  a  multiple  series  connection. 

Periodicity  of  Alternation. — The  rate  of  succession  of  al- 
ternations per  second,  or  per  minute.  The  frequency. 

Polyphase  Current. — Currents  that  constantly  differ  from 
each  other,  due  to  their  proportion  of  periods  of  alter- 
nation, and  adapted  to  polyphase  motors. 

Proposed  Definition  for  2,000  Candle  Power. — An  arc 
whose  maintenance  will  require  450  watts. 

E 

Rheostat. — Will  adjust  the  resistance  without  opening  the 
circuit. 

S 

Standard  Ohm. — A  piece  of  pure  copper  wire  one  circular 
mil  in  diameter,  and  one  foot  long  at  a  certain  tempera- 
ture. 

Static  Electricity. — Electricity  generated  by 'friction. 

V 

Volt. — The  practical  unit  of  electromotive  force.  An  E. 
M.  F.  that  would  cause  a  current  of  one  ampere  to  flow 
through  a  resistance  of  one  ohm. 

W 

Water  Horse-Power. — The  power  developed  by  15  cubic  feet 
of  water  falling  through  a  distance  of  one  foot  per  second. 

Watt. — The  practical  unit  of  electric  activity,  rate  of  work, 
or  energy.  A  watt  equals  44.25  foot  pounds  of  work  done 
per  minute,  or  0.7375  foot-pounds  of  work  done  per  sec- 
ond. 

Watt-Hour. — Unit  of  electric  work.  One  watt  exerted  or 
expended  for  one  hour. 


INDEX 

A 

Absolute  Pressure   57 

Absolute  Zero   40 

Absorption  System  of  Refrigeration   97-98 

Acceleration  of  Gravity 25 

Adiabatic  Curve .58-59 

Air  Compressors   85-89 

Air  Compression  at  High  Altitudes 88 

Air  Compression — Methods  of  85,  86,  87 

Air  Required  for  Combustion 33 

Alternator    114 

Alternating  Current  111-118 

Ammeter    161 

Ampere 108-161 

Angular  Advance  52 

Anhydrous  Ammonia   93-94 

Armature  Construction   121-148 

Armature  Troubles  148-152 

Armature  Winding  133-148 

Atlas  Water  Tube  Boiler .» 12-13 

B 

Babcock  and  Wilcox  Boiler 8-9 

Back   Pressure 57 

Bigelow  Hornsby  Boiler 10-11 

Blow  Off  Pipe  and  Cock 22-27 

Boiler  Material    15 

Boiler  Setting  and  Equipment  19-25 

Boyles  Law 58 

Brick  for  Boiler  Setting . . 19 

Brine  System  of  Refrigeration 96-97 

Brushes— How  to  Set 151-152 

Buck   Stays 20 

Bursting  Pressure—Rule  for 18-37 

i 


ii  Index 

c 

Cahall  Water  Tube  Boiler  7-8 

Calculating  Pump  Capacity  24-25 

Calorific  Valve  of  Fuel 40 

Calorimeter    44 

Care  and  Operation  of  Boilers  31-38 

Causes  of  Poor  Combustion 38 

Chimneys 29 

Circuit  Breaker 163 

Classes  of  Mechanical  Stokers   28 

Cleaning  Fires 31-32 

Coal — Composition  of  39 

Combustion  Chamber  6,  7,  20 

Combustion — Heat 39-42 

Compound  Dynamo   116 

Compression    52-54 

Compound  Engines    47,  49-50 

Condensers 48,  75-76 

Condensing  Engine    47 

Condenser  Pressure  57 

Conservation  of  energy 107 

Coulomb    108-161 

Co  2 — Meaning  of     39 

Curtis  Steam  Turbine  71-72 

Current  Phase   120 

Cut-off 53-54 

D 

Dead  Center   54 

Direct  Current 111-117 

Dished  Heads   17 

De  Laval  Steam  Turbine  72-73 

Definitions— Electric    167-173 

Definitions — Steam .57-59 

De  Lavergne  Ice  Machine 96 

Domes  and  Mud-Drums  22 

Draft  Gauge 44 

Drum  Winding  115 

Dry  Air  Pump   76 

Duplex  Water  Tube  Boiler 13-14 


liidex  iii 

Duties  of  an  Engineer  31-32 

Dynamics 59 

Dynamo-Principle  of 110-111. 

Dynamo — Construction 112-114 

Dynamotor 154 

E 

Eccentric    52-53 

Economizers    40 

Efficient  Joint 16 

Electricity  for  Engineers 107-165 

Electric  Circuit 110 

Electric  Motor 116-117 

Elevators— Electric  and  Hydraulic  99-105 

Erie  City  Water  Tube  Boiler 14 

Equivalent 46 

Evaporation  Tests    43-46 

Exhaust  Injector 28 

Expansion  Curve  59 

F 

Factor  of  Safety 18 

Failure  of  Joints 16-17 

Feed  Pipes  , 23 

Feed  Pumps  22-24 

Feed  Water  Heaters 22,  27-29 

Field  Rheostat   114 

Flue  Gas  Analysis  45 

Foaming 34 

Force   59 

Former  Coils 143 

Friction— Laws  of 65-66 

Frequency — Electric 162 

Fusible  Plugs    21 

G 

Galvanometer 164 

Gas  Engines  77-83 

Gas  Engine  Indicator  83 

Gas  Engine  Igniter 82 


iv  Index 

Gas  Producers 83 

Gauge  Pressure 57 

Governor    , 55 

Grate  Surface  20 

Grounded  Circuit 150 

Gusset  Stays  17 

H 

Hamilton-Holzwarth  Steam  Turbine 73-74 

Heat 40 

Heat  Unit 41 

Heine  Water  Tube  Boiler 8 

Horizontal  Tubular  Boiler   5 

Horse  Power  58 

Hydraulic  Elevator 100-105 

I 

Imperfect  Combustion    33 

Indicator 61-63 

Indicated  Horse  Power 58 

Induction — Laws  of ,110 

Ingersoll-Rand  Air  Compressor 88-89 

Initial  Pressure 57 

Injector    23-24 

Isothermal  Curve 59 

J 
Joule 108 

K 
Kilo-Watt , Ill,  161 

L 

Lap 53 

Latent  Heat 41 

Lead 52-55 

Lightning  Arresters 164-165 

Linde  Ice  Machine , 95 

Low  Water — What  to  do  in  Case  of 34 

Lubrication   .  ,., 65-67 


Index  T 

M 

Magnet 109 

Magnetic  Circuit   110 

Marzolf  Water  Tube  Boiler 13 

Maxim  Water  Tube  Boiler 9-10 

Mean  Effective  Pressure 58 

Mechanical  Draft — Systems  of  28-29 

Mechanical  Equivalent  of  Heat  41 

Mechanical  Stokers 28-29 

Momentum 59 

Motion — First  Law  of 59 

Motor  Armatures , 146-148 

O 

Ohm 108-161 

Ohm's  Law 161 

Oil   Switches    163 

Open  Circuit 151 

Otis  Geared  Traction  Elevator  99-101 

Otis  Traction  Elevator 99 

P 

Piston  Displacement 58 

Piston  Speed   v 58 

Pitch  of  Boiler  Rivets  ! ..15-16 

Pop  Valve   21 

Potential 110 

Power    59 

Principles  of  Boiler  Construction 14 

R 

Radius  of  Eccentricity 52 

Ratio  of  Expansion    57 

Rateau  Steam  Turbine 74 

Reidler-Stumpf  Steam  Turbine 74-75 

Refrigeration    91-98 

Ring  Winding 1 115 

Rotary  Converters 154-162 

Rules  for  Firing  . . . , 31-32 


vi  Index 

S 

Safety  Valves   33 

Series  Dynamo 116 

Short  Circuit — How  to  Locate 150-151 

Shunt  Dynamo 115 

Simple  Engine 47 

Specific  Heat  41 

Steam 41-42 

Steam  Engines 47-70 

Steam  Gauge 21 

Steam  Headers  24 

Steam  Turbines 69-76 

Switch  Boards 159-164 

Synchronizer    158 

T 

Tensile  Strength   14-15 

Terminal  Pressure 57 

Theoretical  Duty  of  Steam 59 

Thermodynamics — First  Law  of 59 

Thermodynamics — Second  Law  of 91 

Through  Stay  Rods 17 

Total  Heat  of  Evaporation  46 

Transformers    153-154 

Triumph  Ice  Machine  96 

Types  of  Boilers 5 

Types  of  Valves  51 

U 

Unit  of  Work    108 

Unit  of  Power    108 

V 

Vacuum   58 

Valve  Travel 52 

Valves  and  Valve  Setting    51-50 

Valves  for  Boiler  Connections    24 

Volt 108,  161 


Index  vii 

W 

Washing  Out  Boiler     35-36 

Water — Composition  of    41 

Water  Column 20-21,  36 

Water  Tube  Boiler   5-6 

Watt   108-109 

Watt  Meter   161 

Westinghouse-Parsons  Steam  Turbine 71 

Wickes  Water  Tube  Boiler 11-12 

Work    ,  59 


The  Calculation  of  Horse 
Power  Made  Easy  :   :   : 

By  L.  ELUOTT  BROOKES 

Author  of   "Gas   and  Oil   Engine    Hand-Book," 
"The  Automobile  Hand-Book,"  Etc. 

Size,  5x7%.     80  Pages,  Illustrated.    Cloth,  75  Cents 

THIS  work  deals  in  a  practical  and  non- 
technical manner  with  the  calculation 
of  the  power  of  Steam  Engines,  *Explo- 
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Particular  attention  has  been  given  to  the 
full  explanation  of  the  elementary  principles 
upon  which  the  calculations  are  based. 

It  has  been  the  endeavor  to  present  in  as 
simple  a  manner  as  is  possible,  a  number  of 
useful  rules  and  formulas  that  may  be  of 
great  value  to  ENGINEERS,  MACHINISTS  and 
DESIGNERS  in  calculating  horse  power. 

Rules  for  plotting  steam  engine  diagrams 
by  arithmetical,  geometrical  and  graphical 
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the  method  used  in  plotting  the  diagram  of 
an  explosive  motor. 

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cut-off  and  average  steam  pressure,  Horse  Power  of  Explosive  Motors,  Degree 
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Steam  Engines  and  Explosive  Motors,  also  tables  of  Average  Steam  Pressure, 
Areas  of  Circles,  Squares  of  Diameters  of  Circles,  Natural  Logarithms  of  Num- 
bers, Thermo-dynamic  Properties  of  Gasoline  and  Air,  Common  Logarithms 
of  Numbers,  and  Mensuration  of  Surface  and  Volume. 


The  term  "  Explosive  Motor  "  includes  Gas,  Gasoline  and  Oil  Engines. 

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ELEMENTARY  ELECTRICITY 

UP   TO    DATE 

By  SIDNEY  AYLMER-SMALL,  M.  A.  I.  E.  E. 


r] 
i 


[IS  book  opens  up  the  way  for 
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types  of  apparatus  for  producing  it, 
all  of  which  are  plainly  described  and 

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governing  their  action  clearly  explained  and  illustrated.  •  The  subject  of 
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electrical  work,  power  and  efficiency  is  the  topic,  and  where  the  genera- 
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Practical  Armature 
and  Magnet  Winding 

By  HENRY  C.  HORSTMANN  and  VICTOR  H.  TOUSLEY 


W 


'HILE  the  subject  of  armature  wind- 
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OPERATORS'  WIRELESS  TELEGRAPH 
1  AND  TELEPHONE  HAND-BOOK 

By  VICTOR  H.  LAUGHTER 


I  TP-TO-DATE  and  most  com- 
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Twentieth  Century 
Machine  Shop  Practice 

By  L.  ELLIOTT  BROOKES 

The  best  and  latest  and  most 
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DYNAMO  TENDING 


for 

ENGINEERS 

Or,  ELECTRICITY 
FOR  STEAM  ENGINEERS 

By  HENRY  C.  HORSTMANN  and 

VICTOR  H.  TOUSLEY, 
Authors  of  "Modern  Wiring  Diagrams  and 
Descriptions  for  Electrical  Workers." 


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come  In  contact  with  the  electrical  apparatus  such  as  pertains  to  light 
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round  corners,  red  edges. 

PRICE $1.50 _^ 

N.  B. — This  is  the  very  latest  and  best  book  on  the  subject  in  print. 

Sold  by  Booksellers  generally  or  sent  postpaid  to 
any  address  upon  receipt  of  price  by  the  Publishers 

FREDERICK  J.  DRAKE  &  CO. 

CHICAGO.  U.S.  A. 


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